Computer Hardware

Its all junk

Buggy, glitchy, intermittant junk. Even when you have assembled hundreds of systems. It’s almost impossible to detect eventual terminal faults within warranty period.

In my opinion, PSU’s (Power supply unit) are partially to blame. Their instability has been demonstrated on more than one occasion.

This has been known to ‘stress’ components to electronical breaking point.

I know who to blame

However the manufacturer of the hardware in question is also to blame.

Because they failed to design sufficient protection from unstable PSU’s into their design.

All manufacturers minimize expendeture to maximize profits.

Manufacturing with a component that has better power handling capabilities costs more.

Cheaper components that only ‘just’ handle the loads are used instead. As a result the hardware may ‘just’ be within specifications.

Prolonged use will normally result in premature failure of the hardware.

Who has a blown up p4 mainboard?

These days, timed electronic failure, in designed into our hardware.

I see failed P4 motherboards.

Everyone has second hand Intel P4 CPU’s (and they are worth nothing..) But no-one has working second hand P4 motherboards?

Hows the kids pIII going?

Why do the P3 and P2 motherboards still work?

How come the P1, 486, 386, 286, XT and PC still work?

(and earlier… Yes Veronica.. There were pc’s before the IBM! and they still go..)

2013-06-17 Computer, Hardware

My latest purchases from ebay.. :)

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2010-05-20 Computer, Hardware

This page is under heavy construction!

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'''TRS-80''' was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units were rolled out to the stores the third week of December 1977. The line won popularity with hobbyists, home users, and small-businesses. Tandy Corporation's leading position in what ''Byte'' Magazine called the "1977 Trinity" (Apple, Commodore and Tandy) had much to do with Tandy's retailing the computer through more than 3000 of its Radio Shack (Tandy in Europe) storefronts. Notable features of the original TRS-80 included its full-stroke QWERTY keyboard, small size, its Floating Point BASIC programming language, an included monitor, and a starting price of $600. The pre-release price was $500 and a $50 deposit was required, with a money back guarantee at time of delivery. One major drawback of the original system was the massive RF interference it caused in surrounding electronics. This became a problem when it was determined to violate FCC regulations, leading to the Model I's phase out in favor of the new Model III.

By 1979, the TRS-80 had the largest available selection of software in the microcomputer market.


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Announced at a press conference on August 3, 1977 by Tandy Corporation, the Radio Shack TRS-80 Microcomputer (later re-designated the Model I) was Tandy's entry into the home computer market, meant to compete head-on against the Commodore PET 2001 and the Apple II. At $599 for a complete package including computer, keyboard, video monitor, and cassette storage, the computer was the most expensive single product Tandy's Radio Shack chain of electronics stores had ever offered. After the first demonstration of the wire wrapped version of the computer to Charles Tandy, there was a discussion as to the quantity that could be sold. The TRS-80's creators Don French and Steve Leininger both suggested that 50,000 could be sold. They were laughed at. It was decided that the initial production run would be 1,000. Several months later the Company management was still unsure of the computer's market appeal, but raised the initial production run to 3,500, because in Radio Shack President Lew Kornfield's words "When the product fails, we can use it in the stores for inventory control and other purposes." Even on introduction day the planned production run was still 3,500.

Tandy ended up selling over 10,000 TRS-80s in its first month of sales, and an additional 55,000 in the next 4 months. Before its January 1981 discontinuation, Tandy sold more than 250,000 Model Is. By the end of its lifetime, the computer had become affectionately known by its users (and snidely referred to by its detractors) as the “Trash-80”.


The Model I combined the mainboard and keyboard into one unit, in what was to be a common case design trend throughout the 8-bit microcomputer era, although it had a separate power supply unit. It used a Zilog Z80 processor clocked at 1.77MHz (later models were shipped with a Z80A). The basic model originally shipped with 4 KB of RAM, and later 16 KB.


The transfer of information about what keys were being pressed was unusual, in that instead of transferring data via an I/O device or chip, the hardware mapped the keyboard to pre-defined locations in memory, i.e., there was no ‘real’ memory at this location, but performing a read from the keyboard area of the memory map would return the state of a particular set of keys.

A version of the computer was produced which replaced the nameplate with a numeric keypad.

Many users complained about the TRS-80 keyboards, which used mechanical switches and suffered from “Keyboard Bounce”, resulting in multiple letters being typed accidentally. A Keyboard De-Bounce tape was distributed to compensate, which both ignored key contact closures if they were detected within a short time of a contact opening, and slowed down polling of the keyboard. Eventually, this was added to a later ROM revision. The keyboard hardware was also changed to be less vulnerable to bounce.


The TRS-80 was accompanied by a white-on-black display, which was a modified RCA XL-100 black and white television. The actual color of the system was light bluish (the standard phosphor used in black-and white televisions), and green and amber filters or replacement tubes (to make the display easier on the eyes) were a common aftermarket item.

Later models came with a green-on-black display.

Because of bandwidth problems in the interface card that replaced the TV’s tuner, the display would lose horizontal sync if large areas of white were displayed; a simple hardware fix (involving less than half an hour’s work) could be applied to correct that.

The video hardware could only display text at 64 or 32 characters wide by 16 lines of resolution. This was because the video memory system used a single kilobyte of video memory. Seven of the bits of each byte were used to display ASCII characters, with the eighth bit used to differentiate between text and “semigraphics” characters.

Primitive graphics (“text semigraphics,” rather than a true bitmap) could be displayed because the upper 64 characters of the 128 character set displayed as a grid of 2×3 blocks (very similar to Teletext). BASIC routines were provided which could write directly to this virtual 128×48 grid.

The original TRS-80 Model I could differentiate between upper and lower characters in memory, but lower case characters were not displayed on the video display. In order to display the lower case properly on the Model I, one had to solder or clip an eighth memory chip onto the back of one of the existing seven video RAM chips, and then bend up a pin to tap an address line off the system bus. This modification became a popular third-party add-on.

Later models came with the hardware allowing the lowercase character set to be displayed with descenders. The software, however, remained unchanged, and when using standard BASIC programming, no lower case characters could be displayed. A small keyboard driver written in machine language could overcome this shortcoming.

Any access to the screen memory, either by writing to it using the BASIC statement PRINT or accessing the screen memory directly, caused “flicker” on the screen. The bus arbitration logic would block video display while access was given to the CPU, causing a short black line. This had little effect on normal BASIC programs, but fast programs made in assembly language could be affected if the programmer didn’t take it into consideration. Many software authors were able to minimize this effect. Notwithstanding this primitive display hardware, many arcade-style games were available for the Tandy TRS-80.

Cassette tape drive

User data was originally stored on cassette tape. A standard monaural audio cassette deck (Radio Shack model CTR-41) was included with the machine. The cassette tape interface was sensitive to audio volume changes, and the machine only gave the very crudest indication as to whether the correct volume was set, via a blinking character on screen when data was actually being loaded - to find the correct volume, one would sometimes have to attempt to load a program once adjusting volume until the machine picked up the data, then reset the machine, rewind the tape and attempt the load again. Users quickly learned to save a file three or more times in hopes that one copy would prove to be readable. Automatic gain control or indicator circuits could be constructed to compensate for this (fortunately the owner’s manual provided complete circuit diagrams for the whole machine, including the peripheral interfaces, with notes on operation), and there was also an alternative tape interface that one could build in order to receive transmissions from the BBC’s Chip Shop programme in the UK, an experiment in transmitting free software for several different BASIC home microcomputers, in a common tape format, over the radio. A special program (loaded using the conventional tape interface) was needed to access the custom interface over the expansion port and then load the recorded software. Tandy eventually replaced the CTR-41 unit with the CTR-80 which had built-in AGC circuitry (and no volume control). This helped the situation, but tape operation was still unreliable.

TRS-80s with Level I BASIC read and wrote tapes at 250 bits per second (25 bytes per second); Level II BASIC doubled this to 500 bits per second (50 bytes per second).

Some programmers wrote machine language programs that would increase the speed to up to 1500 bits per second without loss in reliability.

For loading and storing data, no hardware controller existed. Instead, the processor created the sound itself by switching the output voltage between two states, creating squarewave audio.

The first models of the Model I also had problems reading from the cassette drives. Tandy eventually offered a small board which was installed in a service center to correct earlier models. The ROMs in later models were modified to correct this.

Expansion interface

An optional (and expensive) Expansion Interface (E/I) provided several important features - the ability to expand up to 48K of RAM, a floppy disk controller, a real-time clock, a second cassette port, a RS-232 port (as an option) and a Centronics parallel printer port.

Originally, one could not print from the Model I without purchasing an Expansion Interface. However, Tandy Corp. soon sold a printer-only Interface for the Model I for approx. 300 Deutschmark in Germany.

The Expansion Interface was the most troublesome part of the TRS-80 system. It went through several revisions (a pre-production version is said to have looked completely different, and to have had a card cage) before on-board buffering of the bus connector lines cured its chronic problems with random lockups and crashes. Its edge card connectors tended to oxidise due to the use of two different metals in the contacts, and required periodic cleaning with a pencil eraser. The unit required a second power supply, identical to that of the TRS-80, and was designed with an interior recess which held both power supplies.

Since the cable connecting the expansion interface carried the system bus, it was kept short (about two inches). This meant that the user had no choice but to place it directly behind the computer with the monitor on top of it. This caused problems if one owned a monitor whose case did not fit the mounting holes. Also, the loose friction fit of the edge connector on the already short interconnect cable created the precarious possibility of disconnecting the system bus from the CPU if either unit happened to be moved during operation.

Floppy disk drives

To use the Model I with a disk operating system, one had to buy the Expansion Interface, which included a single density floppy disk interface. This was based on a Western Digital 1771 single density floppy disk controller chip, but since it lacked a separate external data separator, it was very unreliable in practice.

Much of the unreliability was due to bugs in Radio Shack’s early version(s) of TRS-DOS. The 1771 could not report its status for a short interval (several instruction cycles) after it received a command. A common method of handling this was to issue a command to the 1771, perform several “NOP” instructions, then query the 1771 for command status. Early TRS-DOS neglected to use the required wait period, instead querying the chip immediately after issuing a command, and thus false status was often returned to the OS, causing various errors and crashes. If the 1771 was handled correctly by the OS, it was actually fairly reliable.

Double-density floppy disks

A Data Separator and a Double Density disk controller (based on the WD 1791 chip) were made available from Percom (a Texas peripheral vendor), LNW, Tandy and others. The Percom Doubler added the ability to boot and use Double Density Floppies (they provided their own modified TRSDOS called DoubleDOS), and included the Data Separator. The LNDoubler added the ability to read and write from 8” Diskette Drives for over 1.2mb of Storage.

Double-sided floppy disks

All TRS-80 disk formats were soft-sectored with index-sync (as opposed to the Apple II formats, which were soft-sectored without index sync, with many Apple drives lacking even an index hole detector), and except for some very early Shugart drives (recognizable by their spiral-cam head positioner), all TRS-80 floppy drives were 40-track double-density models. The combination of 40 tracks, double-density, and index-sync gave a maximum capacity of 180 kilobytes per single-sided floppy disk, considerably higher than most other systems of the era. On the other hand, the use of index-sync meant that in order to turn a double-sided disk into a “flippy disk”, it was necessary not only to cut a second write-enable notch, but also to punch a second index hole window in the jacket (at great risk to the disk inside). One could also purchase factory-made “flippies”, or format the back side for Apple systems (as some software publishers of the era did).

The drives sold by Radio Shack were 35-track models with a 160K capacity.

Hard Drive

Radio Shack introduced a 5MB hard-drive unit for the TRS-80. The physical size of the unit was about the same as a modern desk-top computer enclosure. The unit had a retail price of approximately $1500, although it could be purchased for a bit less from some of the non-corporate stores.


One unusual peripheral offered was a “screen printer”: an electrostatic rotary printer that scanned the video memory through the same bus connector used for the E/I, and printed an image of the screen onto aluminum-coated paper in about a second. Unfortunately, it was incompatible with both the final, buffered version of the E/I, and with the “heartbeat” interrupt used for the real-time clock under Disk BASIC. This could be overcome by using special cabling, and by doing a “dummy” write to the cassette port while triggering the printer.

Two other printers were offered: one for 57 mm metal coated paper, selling for approximately 600 Deutschmark in Germany, and one built by Centronics for normal paper, costing at first 3000 Deutschmark, later sold at approximately 1500 Deutschmark in some stores. It had only 7 pins, so letters with descenders such as lowercase “g” did not reach under the baseline, but were elevated within the normal line.


Two versions of the BASIC programming language were produced for the Model I. Level I BASIC fit in 4 KB of ROM, and Level II BASIC fit into 12 KB of ROM. Level I was single precision only and had a smaller set of commands. Level II introduced double precision floating point support and had a much wider set of commands. Level II was further enhanced when a disk system was added, allowing for the loading of Disk BASIC.

Level I Basic was based on Li-Chen Wang’s free Tiny BASIC, additional functions added by Radio Shack. It achieved a measure of noteworthiness due in large part to its outstanding manual, written by David Lien, which presented lessons on programming with text and humorous graphics, making the subjects very easy to understand. It had only two string variables (A$ and B$), 26 numeric variables (A - Z) and one array, A(). Code for functions like SIN(), COS() and TAN() was not included in ROM but printed at the end of the book. The only error messages were: “WHAT?” for syntax errors, “HOW?” for arithmetic errors such as division by zero, and “SORRY” for out of memory errors.

Level I BASIC was not tokenized, reserved words were stored literally. In order to maximize the code that could be crammed into 4K of memory users could enter abbreviations for reserved words. For example, writing “P.” instead of “PRINT” thus saving 3 bytes.

Level II BASIC was licensed from Microsoft. It was a cut-down version of the 16 KB Microsoft BASIC (Extended BASIC), since the Model I had 12 KB of ROM space. The accompanying manual was not nearly as colorful and suited for beginning programmers as the Level I BASIC manual. Original Level I BASIC-equipped machines could be retrofitted to Level II through a ROM replacement performed by Radio Shack for a fee (originally $199 in 1978 dollars). Users with Level I BASIC programs stored on cassette had to convert these to the non-tokenized Level II BASIC before use. A utility for this was provided with the Level II ROMS.

The Disk Based BASIC added the ability to perform disk I/O, and in some cases (NewDos/80, MultiDOS, DosPlus, LDOS) added powerful sorting, searching, full screen editing, and other features. Level II BASIC recognized some of these commands and issued a “?L3 ERROR”, suggesting that a behind-the-scenes change of direction intervened between the recording of the Level II ROMs and the introduction of Disk BASIC, which Radio Shack didn’t call Level III.

Microsoft also marketed a tape-cassette based enhanced BASIC called Microsoft Level III BASIC programming language (Level III BASIC). This added most of the functions in the full 16 KB version of BASIC.

Software applications

A wide range of software applications were available for the TRS-80. Many leading developers, and independent software companies such as Big Five, produced unlicensed versions of popular arcade hits like Namco’s Pac-Man and Galaxian, Atari’s Centipede, Sega’s Zaxxon and Stern Electronics’ Berzerk (with digitized speech). Some companies ported games from other home computers of the era, such as the original Zork adventure game. There were also many games unique to the TRS-80, including shooters like Cosmic Fighter and Defence Command and strange experimental programs such as Dancing Demon, which was not strictly speaking a game but did have significant entertainment value.

A full suite of office applications were also available, including the VisiCalc and As-Easy-As spreadsheets and the Lazy Writer, Electric Pencil and Scripsit word processors.

Utility software such as Stewart Software’s Toolkit offered the first sorted directory, decoding or reset of passwords, and the ability to eliminate parts of TRS-DOS that were not needed in order to free up floppy disk space. They also produced the On-Line 80 BBS, a TRS-DOS based Bulletin Board System.

TRS-DOS—Radio Shack’s operating system for its TRS-80 computers—had significant limitations, opening the market for various alternative OSes, including NewDOS, a third-party rival sold by a company called Apparat Personal Computers, which went out of business in 1987. Others included DoubleDOS, DOSPlus, LDOS, MicroDOS, NEWDOS/80, UltraDOS, later called Multidos, and VTOS. The last versions (6.x) of TRSDOS were actually re-named LS-DOS (aka, LDOS).


Many clones of the Model I came on the market: the Lobo Max-80 (Lobo also produced their own version of the Expansion Interface), the LNW-80 Models I/II and Team computers (LNW also produced an alternate version of the Expansion Interface), and the Dutch Aster CT-80, a computer that could run both TRS-80 and CP/M software, and also had all the improvements of the later Model III.

EACA in Hong Kong made a Model I clone that was marketed around the world under different names with modifications. In Australia and New Zealand it was the Dick Smith System-80, in North America it was PMC-80 and PMC-81, in Hungary the HT-1080Z, in South Africa the TRZ-80, and in Western Europe it was Video Genie. The expansion bus was different and EACA also made its own Expansion Interface to fit it. There were several versions, and it was later split into a ‘home’ and a ‘business’ version, Genie I and II, and System-80 Mark I and II, where the II would have a numeric keypad instead of the built-in cassette player. EACA’s Colour Genie was also based on TRS-80 Model I but with improved graphics and other changes, reducing its compatibility.

In Brazil several manufacturers developed clones for models I/III/IV. Dismac series D8000/D8001/D8002 (all three Model I clones) were the first personal computers manufactured in industrial scale in South America. Digitus made the DGT-100 and DGT-1000, Prologica made the highly-successful P500 series (both Model III clones), Sysdata Eletrônica Ltda. made the Sysdata Jr. Prologica also made the CP400 / CP 400II which were copies of the TRS-80 Color Computer, with the external case being almost a copy of the Timex Sinclair 2068.

In Germany, S.C.S. GmbH in Mörfelden- Waldorf offered the Komtek-I Model I clone. Noteworthy was its four relay switching outputs.

In Soviet Union, some ideas from TRS-80 was used in development of Корвет (Corvette) home/school computer.

Other Radio Shack/Tandy Computers

Tandy 10

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The Tandy 10 was the second computer introduced by Radio Shack, although it wasn’t part of the TRS-80 line. It was actually manufactured by Applied Digital Data Systems, also known as ADDS. ADDS (which still exists today as Boundless Technologies) was the largest independent supplier of video display terminals at the time. The Tandy 10 was the only Radio Shack computer to use the Tandy name (Radio Shack’s parent company) until the mid 1980’s.

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First offered in 1978, the Tandy 10 (catalog number 81-2110) was actually the ADDS System 50, a variant on the earlier System 70. Described as a workstation, the Tandy 10 was clearly targeted at businesses. It had a good set of features for a computer at that time:

* an 8080 processor (a predecessor to the Z80 used in the Model I)
* 48K of RAM
* a 51 key keyboard with an 11 key numeric keypad and 24 function keys
* an 80 by 24 text display, supporting upper and lower case, blinking, underlining, reverse video, and half intensity
* two double-sided floppy drives
* extended “Dartmouth BASIC”
* ADOS (ADDS Disk Operating System)
* integration into its own metal desk, described as “Desk Packaging”

The Tandy 10 itself cost $9,995.00. There were also two other fees attached to the computer:

  • a local installation fee of $150.00
  • a local maintenance fee that ranged from $100.00 to $125.00

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Radio Shack offered a number of options for the Tandy 10 including:

* Fortran compiler for $300.00
* 60 characters-per-second 80 column printer (catalog 26-1152) for $1,559.00
* 120 character-per-second 132 column printer (catalog 88-1001) for $2,295.00
* 180 character-per-second 132 column printer (catalog 88-1003) for $2,995.00

Radio Shack sold very few Tandy 10 computers. It was discontinued by 1980 and remains mostly forgotten today.

Model II

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In October 1979, Tandy began shipping the ''Model II'', which was targeted to the small-business market. It was designed as a replacement to the Tandy 10 and offered business users what was viewed as a more robust hardware platform compared to the Model 1. Built using the faster Zilog Z80A chip running at 4MHz, 8" floppy disk drive, and monochrome 80x24 monitor built into a single cabinet, DMA and vectored interrupts that the Model I lacked, and a detached keyboard. It was available with 32 KB or 64 KB of RAM; two RS-232 serial ports and a Centronics printer port were standard. Unlike the Model I, the video and keyboard were not memory-mapped, leaving the entire memory space available for programs. Hard disk drives and additional floppy drives were available as options. The Model II ran the TRSDOS-II operating system and BASIC. TRSDOS-II was not very compatible with TRSDOS for the Model I, thus the Model II never had the same breadth of available software as the Model I. This was somewhat mitigated by the availability of the CP/M operating system for the Model II from third parties such as Pickles & Trout.

Tandy offered a desk custom-designed for the Model II for US$370. It could hold an additional three 8” disk drives or up to four 8.4MB hard drives.

The Model II was later replaced by the Model 12, which was essentially a Model 16B (described below) without the Motorola processor and other features such as an expansion cage. Customers could choose to later upgrade a Model 12 to a Model 16B.

Model III

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As a follow-on to the Model I, in July 1980 Tandy released the ''Model III'', a more integrated and much improved system. The improvements of the Model III included built-in lower case, a better keyboard, and a faster (2.03MHz) Z-80 processor. With the introduction of the Model III, Model I production was eventually discontinued as the Model I systems did not comply with new Federal Communications Commission regulations regarding radio interference. In fact, the Model Is radiated so much Radio Frequency Interference that many games were designed so that an Amplitude modulation|AM radio next to the computer could be used to provide sounds.

The TRS-80 Model III also came with the option of integrated disk drives. Since they took power from the same supply as the motherboard and screen, which was not upgraded for the disk drive models, it was common to see the screen image shrink noticeably during drive access.

Model 4

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The successor to the Model III was the Model 4 (April 1983, with "4" written as an Arabic numeral), which included the capability to run CP/M. Running CP/M had previously only been possible via a hardware modification that remapped the BASIC ROMs away from memory address zero, such as the third-party add-on sold as the Omikron Mapper board, or by running a version of CP/M modified to run at a starting address other than zero. However, this also required modified applications, since the area of memory at zero contained the vectors for applications to access CP/M itself. The Model 4 also added an 80 column by 24 line video display mode required for CP/M compatibility.

The Model 4 shipped with TRSDOS 6, an enhanced version of LDOS by Logical Systems and a vastly superior operating system to Tandy’s earlier TRSDOS offerings. When the Model 4 booted into TRSDOS 6 the video display switched into 80x24 mode and the entire 64KB address space was mapped as RAM. The Model 4 was also capable of running all Model 3 software when a Model 3 operating system disk was detected and loaded during bootup with a 64x16 video mode and Model 3 ROMs mapped from address zero.

The Model 4 also had the ability to display 640x240 or 512x192 high-resolution monochrome graphics with an optional board. A “luggable” version known as the Model 4P (1983) was a self-contained unit with a case design similar to that of a portable sewing machine.

Early versions of the Model 4 mainboard were designed to accept a Zilog Z8000 16 bit CPU upgrade board to replace the Z80 8 bit CPU but this option was never released.

Model 4P

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Model 4P can use all Model 4 disk software. It can also run all Model III TRSDOS and LDOS disk programs (in Model III mode) without change. Model 4P is compatible with the CP/M Plus operating system. Model 4P features a full 80-character by 24-line 9″ green-screen display that can be upgraded to provide optional 640×240 high-resolution graphics. The full-size keyboard features CONTROL, CAPS and three function keys. An internal direct-connect modem board was offered as an option.

Model 4D

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The Tandy Model 4D is the last and most powerful Model 4 made. It is similar to the standard Model 4, except that it has double-sided disk drives, and an improved gate-array mainboard. Note that it now bears the TANDY name instead of TRS-80. One small but handy improvement is that the serial port has been redirected to be accessable from the back of the machine. This computer made its first appearance in the 1987 Tandy Computer Catalog.

Model 12

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The Tandy TRS-80 Model 12 was a business system intended to replace the Model II which was widely used as an accounting and management system by numerous small companies. Unlike Model II, it was a single board system with a white case instead of the typical dark grey one of previous TRS-80 models. It could be expanded by adding an optional card cage in which six expansion cards could be inserted, for example the monochrome high resolution card. However it was fully compatible with most popular Model II business programs. The Model 12 was one of the first computer equipped with the new slim line 8" double side / double density floppy drive that could store 1.25 MB, twice as much as the Model II full-size version.

For faster operation, the main board could be exchanged with the 16-bit Tandy 68000 one. The computer thus became fully compatible with the Tandy Model 16 and so could run Unix operating system variants.

Model 16a

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Tandy later released the ''TRS-80 Model 16'', as the follow-on to the Model II; an upgrade kit was available for Model II systems. The Model 16 added a 6 MHz, 16-bit Motorola 68000 processor and memory card, keeping the original Z-80 as an I/O processor. It could run either TRSDOS-16 or Xenix, Microsoft's version of UNIX. Of the two operating systems, Xenix was far more popular. TRSDOS-16 was essentially Model II TRSDOS, with no additional features and little compatible software. 68000 functionality was added as an extension, loading 68000 code into the 68000 memory via a shared memory window with the Z80.

Xenix, on the other hand, offered the full power of UNIX System III including multi-user support. The Model 16 family with Xenix became a popular system for small business, with a relatively large library of business and office automation software for its day. Tandy offered multi-user word processing Scripsit 16, spreadsheet Multiplan, and a 3GL “database” (Profile 16, later upgraded to filePro 16+), as well as an accounting suite with optional COBOL source for customization. RM-COBOL, Basic, and C were available for programming, with Unify and Informix offered as relational databases. A kernel modification kit was also available.

TRS-Xenix was notable for being a master/slave implementation, with all I/O being performed by the Z80 while all processing was done within the otherwise I/O-free 68000 subsystem.

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The DT-1 was a Data Terminal used with the Model 1, 2, 3, or 16. It has: A 70 key console keyboard that includes a 12-key numeric pad and conforms to the standard Data Terminal keyboard format, A 12-inch screen, Both serial and parallel printer interface, RS-232-C interface, Software selectable "switches" to toggle various options. (++)

Model 16b/Tandy 6000

The Model 16(a) evolved into the Model 16B, and then the Tandy 6000 HD, gaining an internal hard drive along the way and switching to an 8MHz 68000 and half-height, 8-inch floppy drives (double-sided, double density, 1.2 MB). The Model 12, Model 16B, and 6000 HD all used the same white interchangable casing. Tandy offered 8.4MB, 15 MB, 35 MB, and 70 MB external hard drives, up to 768 KB of RAM, and up to six additional RS-232 serial ports supporting multi-user terminals. Additional memory and serial port expansion options were available from aftermarket companies.

Internal variants of the Model 16 architecture were built running at speeds in excess of 10 MHz, 68010 processors, up to 8Mb of RAM, SCSI disk interfaces, and up to 12 RS-232 ports.

Other systems

Color Computers

CoCo 1

The Radio Shack TRS-80 Color Computer (also called Tandy Color Computer, or CoCo) was a home computer launched in 1980. Despite the name, the “Color Computer” was a radical departure from earlier TRS-80 Models - in particular it had a Motorola 6809E processor, rather than the TRS-80’s Zilog Z80.

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The Motorola 6809E was a very advanced processor, but was correspondingly more expensive than other more popular microprocessors. Competing machines such as the Commodore VIC-20, the Commodore 64, the Atari 400, and the Atari 800 were designed around a combination of the much cheaper MOS 6502, itself essentially a clone of the Motorola 6800, paired with dedicated sound and graphics chips and were much more commercially successful in the 1980s home computer market. Steve Wozniak once commented that the 6502 was 1/4 the price of the Motorola 6800 when the original Apple was being developed in the late 70s. By 1986 prices for 8 bit processors had dropped dramatically from the late 70s, but the MC6809 was still just over twice the price of a MOS6502 (6809/6809E - $5.95; MOS6502 - $2.79). The initial model (catalog number 26-3001) shipped with 4K of Dynamic Random Access Memory (DRAM) and an 8k Microsoft BASIC interpreter in ROM. Its price was $399. Within a few months, Radio Shack stores across the US and Canada began receiving and selling the new computer.

Initial versions of the CoCo were upgraded to 32K by means of piggybacking two banks of 16K memory chips and adding a few jumper wires. A later motherboard revision removed the 4K RAM option and were upgraded to 32K with “half-bad” 64K memory chips as a cost-cutting measure. These boards have jumpers marked HIGH/LOW to determine which half of the memory chip was good. This was transparent to the BASIC programmer since in either configuration 32K of memory was available. As memory production yields improved and costs went down, many (perhaps most) 32K CoCo 1s were shipped with perfectly good 64K memory chips; many utilities and programs began to take advantage of the “hidden” 32K. Eventually the 32K memory option was dropped entirely and only 16K or 64K versions were offered. All versions that shipped with standard Color BASIC could be upgraded to Extended BASIC by simply plugging a ROM into an empty socket provided on the motherboard. Toward the end of the CoCo 1 production run, some models shipped in a white case with a modified keyboard, often referred to as the “melted” keyboard, which had bigger keycaps but a similar rubbery feel.

CoCo 2

During the CoCo 1 production run, much of the discrete support circuitry had been re-engineered into a handful of custom integrated circuits, leaving much of the circuit board area of the CoCo 1 as empty space. To cut production costs, the case was shortened by about 25% and a new, smaller power supply and motherboard were designed. The “melted” keyboard from the white CoCo 1 and the TDP-100 style ventilation slots were carried over. Aside from the new look and the deletion of the 12 volt power supply to the expansion connector, the computer was essentially 100% compatible with the previous generation. The deletion of the 12 volt power supply crippled some peripherals such as the original floppy disk controller, which then needed to be upgraded, installed in a Multi-Pak interface, or supplied with external power.

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Production was also partially moved to Korea during the CoCo 2's life-span, and many owners of the Korean-built systems referred to them as "KoKos". Production in the USA and Korea happened in parallel using the same part numbers; very few, if any, differences exist between the USA built and Korean built CoCo 2 machines. Upgraded BASIC ROMs were also produced, adding a few minor features and correcting some bugs. A redesigned 5-volt disk controller was introduced with its own new Disk BASIC ROM (v1.1). This controller added the "DOS" command which was used to boot the OS-9 operating system by Microware. Later in the production run, the "melted" keyboard was replaced with a new, full-travel, typewriter-style keyboard.

The final significant change in the life of the CoCo 2 was made for the models 26-3134B, 26-3136B, and 26-3127B (16K standard, 16K extended, and 64K extended respectively). Internally this model was redesigned to use the enhanced VDG, the MC6847T1. This enhanced VDG allowed the use of lower case characters and the ability to change the text screen border color. However, for compatibility reasons neither of these features were used and are not enabled in BASIC. Midway during the production run of these final CoCo 2s, the nameplate was changed from “Radio Shack TRS-80 Color Computer 2” to “Tandy Color Computer 2”. The red, green, and blue shapes were replaced with red, green, and blue parallelograms.

CoCo 3

On July 30, 1986, Tandy announced the Color Computer 3 at the Waldorf-Astoria Hotel in New York City. This new model of the Color Computer line was meant to better compete with the Apple II GS, Commodore Amiga and Atari ST systems.[dubious – discuss] It came with 128K of RAM, which could be upgraded to 512K. The keyboard surround and cartridge door plastic were changed from black to grey. The keyboard layout was revised, putting the arrow keys in a diamond configuration and adding CTRL, ALT, F1 and F2 keys. It sold in Radio Shack stores and Tandy Computer Centers for $219.95.

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The CoCo 3 was compatible with most of the CoCo 2's peripherals. Most older software ran on it. Taking the place of the graphics and memory hardware in the CoCo 1 and 2 was an application-specific integrated circuit (ASIC) called the "GIME" (Graphics Interrupt Memory Enhancement) chip. The GIME also provided additional features: Output to a composite video monitor or analog RGB monitor, in addition to the CoCo 1 and 2's TV output. This did much to improve the clarity of its output. A paged memory management unit which broke up the 6809's 64k address space into 8x8K chunks. Although these chunks were considered to be too large by many programmers, the scheme would later allow third party RAM upgrades of up to 2 MB (256x8k).

Text display with real lowercase at 32, 40, 64, or 80 characters per line and between 16 and 24 lines per screen. Text character attributes, including 8 foreground and 8 background colors, underline, and blink. New graphics resolutions of 160, 256, 320 or 640 pixels wide by 192 to 225 lines. Up to 16 simultaneous colors out of a palette of 64 displayable at one time (unless programming tricks were employed to display more). Omitted from the GIME were the seldom-used SAM-created Semigraphics 8, 12, and 24 modes. A rumored 256 color mode (detailed in the original Tandy spec for the GIME)[2] has never been found.

Previous versions of the CoCo ROM had been licensed from Microsoft, but by this time Microsoft was not interested in extending the code further.[citation needed] Instead, Microware provided extensions to Extended Color BASIC to support the new display modes. In order to not violate the spirit of the licensing agreement between Microsoft and Tandy, Microsoft’s unmodified BASIC software was loaded in the CoCo 3’s ROM. Upon startup, the ROM is copied to RAM and then patched by Microware’s code. Although this was a clever way of adding features to BASIC, it was not without some flaws: the patched code had several bugs, and support for many of the new hardware features was incomplete.

Model 100 line

In addition to the above, Tandy produced the TRS-80 Model 100 series of “laptop” computers. This series comprised the TRS-80 Model 100, Tandy 102, Tandy 200 and Tandy 600. The Model 100 was designed by the Japanese company Kyocera with software written by Microsoft. It is reported that the Model 100 featured the last code that Bill Gates ever wrote.

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The Model 100 had an internal 300 baud modem, built-in BASIC, and a limited text editor. It was possible to use the Model 100 on essentially any phone in the world with the use of an optional acoustic coupler that fit over a standard telephone handset. The combination of the acoustic coupler, the machine's outstanding battery life (it could be used for days on a set of 4 AA batteries), and its simple text editor made the Model 100/102 popular with journalists in the early 1980s. The Model 100 line also had an optional bar code reader, serial/RS-232 floppy drive and a Cassette interface.

Also available as an option to the Model 100 was an external expansion unit supporting video and a 5 1/4” disk drive. It is connected via the 40-pin expansion port in the bottom of the unit.

Tandy 102

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The last refresh to the product line was the Tandy 102, introduced in 1986 as a direct replacement for the Model 100, having the same software, keyboard and screen, and a nearly identical, but thinner, form factor. Minimum memory was 24 KB RAM.


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Still sought after by writers and students, the Tandy WP2 and Tandy WP3 (Identical units, the latter marketed in Canada only) are perfect writing companions. These machine are full computers with similar capabilities to the Tandy 102. If you are still in school and are tired to having to hog the back row of the classroom to plug in your notebook, pick up a Tandy WP2 and you can run 20 hours continuous on just 4 AA batteries.

Tandy 200

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The ''Tandy 200'' was introduced in 1984 as a higher-end complement to the Model 100. The Tandy 200 had 24 KB RAM expandable to 72 KB, a flip-up 16 line by 40 column display, and a spreadsheet (Multiplan) included. The Tandy 200 also included DTMF tone-dialing for the internal modem. Although less popular than the Model 100/102, the Tandy 200 was also particularly popular with journalists in the late 1980s and early 1990s.

Tandy 600

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The last new model that could be considered part of this line was the Tandy 600, introduced in October 1985. Similar to the Tandy 200, it featured a flip-up screen, but with 80 columns rather than 40. Built-in features included a 3.5" diskette drive, rechargeable batteries, and 32K of RAM expandable to 224K. The underlying software platform was Microsoft's 16-bit Hand Held Operating System (Handheld DOS or HHDOS), along with word processing, calendar, database, communication and spreadsheet software. Unlike earlier models, BASIC was an extra-cost option rather than built in.[

Tandy FD1100

Model: Tandy 1110 FD First Released: 1992 CPU: 8/8bit NEC V20 @ 10 Mhz. RAM: 640K ROM: 32K for Bios Ports: One serial ports, One parallel port Display: LCD super-twisted nematic, green Chip Set MN5504 LCD CGA emulation Storage: 720K 3.5” Floppy, 20MB IDE Hard Drive. Weight: 6.6 Lbs Battery: Lead-acid rechargeable, 3.5 Hrs. Operating System: DeskMate Interface, MS-DOS 3.32 in ROM

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These MS-DOS notebooks were based on the NEC V20 processors. Short lived was the Tandy 1100FD and Tandy 1100HD notebooks however. Released in 1992 the 1100 Series was based on the then popular NEC V20 processor clocked at 10 MHz. These units were short lived due to the fact that competitors were already producing VGA notebooks based on Intel's 16bit processor the 80286. Further Tandy designed these with only two ports with no internal features such as a modem or external video port. This is not to say that the unit was of poor quality. The Tandy 1100 Series was well thought out. With it's DeskMate Interface on ROM that machine took 3 seconds to boot up into MS-DOS 3.3, and you were ready to start to work. In comparison to the TRS-80 Model 100 and 102 the Tandy 1100FD and 1110 HD were positioned to take the same market.

Tandy LT1400

Tandy Corporation announced its new MS-DOS laptop computer November 1987. The LT1400 is a 13.5 lb. computer that has 768K of memory, two front- mounted 720K 3.5” disk drives, and a NEC V20 CPU running at 7.16 MHz. The display is a backlit supertwist LCD. Text on the display is a crisp blue on grey, and is readable at roughly 60 degrees or more to either side. Text is also readable when scrolling, something heretofore unseen on LCD displays. The display has a 640x200 pixel resolution (80x25 text) and a 1:1.4 aspect ratio. The keyboard has a slightly mushy feel, but has excellent tactile feedback. The twelve function keys are arranged along the top. Several keys perform dual functions in lieu of a dedicated numeric keypad. Indicator lights show power, disk drive activity, num lock and scroll lock state. The LT1400 comes standard with serial and parallel ports, as well as RGBI and composite display outputs. An external disk drive port is also included (the LT 1400 can boot off of the external drive if necessary).

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A extra feature is the external keyboard port, which allows the 101-key enhanced keyboard to be directly plugged in and used if you don't like what came with the laptop. The LT 1400 uses rechargeable batteries that are rated at 4 hours of continuous use. However, the batteries are designed to be replaceable, and changing batteries involves merely opening the battery compartment on top of the computer, removing the battery pack and popping in a new one. A "keep-alive" circuit keeps memory refreshed during this operation so that no work is lost. Low power is indicated by a warning beep when 30 to 45 minutes of power remain. Thereafter the beeps become more insistent until finally the machine shuts down.

Unlike the ill-fated Tandy 600, the LT 1400 has a carrying handle, and a soft carrying case is available as an option. Another option for the LT1400 is an internal 1200 baud modem. Third party 2400 baud modems and hard drives are expected to become available presently.

The LT 1400 was priced at $1599, and additional battery packs were $79.95 each.

Tandy 1500 HD

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The Tandy 1500HD, was avaiable from Radio Shack dealers nationwhide. This tablet-sized unit was less than 2 inches thick and weighed under 6 pounds, including its battery and charger. It ran at 10 megahertz, and its standard configuration included 640K of RAM (expandable by another 1 MB for $399.95), a 20MB hard-disk drive, a 3 1/2-inch high-density floppydisk drive, and one serial and one parallel port (but no video-out connection). The battery lasted about three hours per charge depending on frequency of hard disk access. The unit had a full-size 84-key keyboard that provided 101-key emulation. It also has 640-by-200 pixel blue-on-white backlit display that let you select either of two brightness levels. The 1500HD was bundled with Tandy's DeskMate software, which included a word processor, address book, calendar, filer, telecommunications program, and spreadsheet. The unit listed for $1,999 but often was on sale for $1,699.


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The TRS-80 MC-10 was a short-lived and little-known Tandy computer, similar in appearance to the Sinclair ZX81. It was a small system based on the Motorola 6800/6803 processor and featured 4 KB of RAM. A 16 KB RAM expansion pack that connected on the back of the unit was offered as an option as was a thermal paper printer. A modified version of the MC-10 was sold in France as the Matra Alice. Programs loaded using a cassette which worked much better than those for the Sinclair. A magazine was published which offered programs for both the CoCo and MC-10 but very few programs were available for purchase. Programs for the MC-10 were not compatible with the CoCo.

Pocket Computers

A Tandy Pocket Computer is one of a line of 1980s small pocket computers—calculator-sized programmable computing devices—sold primarily under the Tandy, TRS-80 or Radio Shack brands, but were actually rebadged Sharp and Casio devices with different model names. They were given designations from PC-1 to PC-8. The PC-1, -2, -3 and -8 are Sharp devices, while the PC-4, -5, -6 and -7 were designed by Casio.


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* RAM (total): 1,920 bytes
* RAM available: 1,424 bytes
* ROM: ?
* CPU: VLSI specific
* Text screen: 1 line of 24 characters
* Graphic screen: No
* Sound: Yes, not adjustable
* Size: 175 x 70 x 15 mm
* Weight: 170 g. with batteries
* Year: 1980
* Power: 4 button batteries type MR44


  • Printer: 26-3505 Needle technology
  • Storage: 26-3503 External tape interface


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* RAM (total): 2 / 6 / 10 Kb (0 or 1 ramcard of 4 or 8 Kb)
* RAM available: 1,850 / 5,946 / 10,042 bytes
* ROM: 16 Kb
* CPU: LH-5801 8 bits CMOS
* Text screen: 1 line of 26 characters
* Graphic screen: 7 x 156 pixels
* Sound: Tune, duration, and number adjustable
* Size: 195 x 86 x 25 mm
* Weight: 375 g. with batteries
* Year: 1982
* Power: 4 AA alkaline batteries, 6 Volts power adaptor


  • Memory: 26-3615 - 4 Kb, 26-3616 - 8 Kb
  • Printer: 26-3605 4 colors technology
  • Storage: 26-3605 External tape interface
  • I/O: 26-3612 RS-232 interface


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* RAM (total): 2 Kb
* RAM available: 1,438 bytes
* ROM: 24 Kb
* CPU: 8 bits CMOS
* Text screen: 1 line of 24 characters
* Graphic screen: No
* Sound: Only number of beep adjustable
* Size: 135 x 70 x 10 mm
* Weight: 115 g. with batteries
* Year: 198?
* Power: 2 CR-2032 lithium batteries


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* RAM (total): 1 Kb
* RAM available: 544 bytes
* ROM: 12 Kb
* CPU: HD61913A01
* Text screen: 1 line of 12 characters
* Graphic screen: No
* Sound: No
* Size: 165 x 71 x 10 mm
* Weight: 116 g. with batteries
* Year: 1983
* Power: 2 CR-2032 lithium batteries


  • Memory: 26-3653 1 Kb
  • Printer: 26-3652 Thermal technology
  • Storage: 26-3651 External tape interface


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* RAM (total): 4 Kb
* RAM available: 3,552 bytes
* ROM: ?
* CPU: VLSI specific
* Text screen: 1 line of 24 characters
* Graphic screen: No
* Sound: Dual tone beep (high, low)
* Size: 142 x 142 x 9 mm (opened)
* Weight: 161 g. with batteries
* Year: 198?
* Power: 2 CR-2032 + 1 CR-1220 lithium batteries


  • Printer: 26-3652 Thermal technology
  • Storage: 26-3651 External tape interface


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* RAM (total): 8 / 16 Kb (0 to 1 ramcard of 8 Kb)
* RAM available: 7,520 / 15,712 bytes
* ROM: ?
* CPU: VLSI specific
* Text screen: 1 line of 24 characters
* Graphic screen: No
* Sound: Dual tone beep (high, low)
* Size: 142 x 142 x 9 mm (opened)
* Weight: 165 g. with batteries
* Year: 198?
* Power: 2 CR-2032 + 1 CR-1220 lithium batteries


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* RAM (total): 2 Kb
* RAM available: 1,568 bytes
* ROM: ?
* CPU: VLSI specific
* Text screen: 1 line of 12 characters
* Graphic screen: No
* Sound: No
* Size: 180 x 140 x 10 mm (opened)
* Weight: 146 g. with batteries
* Year: 198?
* Power: 2 CR-2032


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* RAM (total): 2 Kb
* RAM available: 1,278 bytes
* ROM: 18 Kb
* CPU: 4 bits CMOS
* Text screen: 1 line of 16 characters
* Graphic screen: No
* Sound: No
* Size: 135 x 70 x 10 mm
* Weight: 95 g. with batteries
* Year: 1986
* Power: 2 CR-2032 lithium batteries


  • Printer: 26-3591 Thermal technology
  • Storage: 26-3591 External tape interface

PC-compatible computers

The Tandy 1000 was followed by a series of models which appended two or three letters to the name, after a space, (e.g. Tandy 1000 EX, Tandy 1000 SX, Tandy 1000 TX, Tandy 1000 RL, Tandy 1000 RLX). In a few instances, a slash and a number or additional letters were appended to these letters (e.g. Tandy 1000 TL/2, Tandy 1000 RL/HD.)

The machine was primarily aimed at the home and educational markets, and it copied the IBM PCjr’s 16-color graphics (PCjr’s graphics were an extension of CGA video) and 3-voice sound, but didn’t use the PCjr cartridge ports. As the Tandy 1000 line outlasted the PCjr by many years these graphics and sound standards became known as “Tandy-compatible” or (for the graphics) “TGA” (standing for Tandy Graphics Adapter) and many software packages of the era listed their support for Tandy standard hardware on the package.

Tandy 1000 computers were some of the first IBM PC clones to incorporate a complete set of basic peripherals on the motherboard using proprietary ASICs, the forerunner of the chipset. All Tandy 1000 computers featured built-in Tandy video hardware with color graphics (CGA compatible with enhancements,) enhanced sound (based on one of several variants of the Texas Instruments SN76496 sound generator), game ports compatible with those on the TRS-80 Color Computer, an IBM-standard floppy disk controller supporting two drives, and a parallel printer port, all integrated into the motherboard. This is in addition to the hardware standard on the IBM PC, PC/XT, and PC/AT motherboards: keyboard interface, expansion slots, memory subsystem, DMA, interrupt controller, math coprocessor socket. (Hard disks were high end, not standard, equipment for home computers until the late years of the Tandy 1000 line, explaining the absence of an integrated hard disk controller from most Tandy 1000 motherboards.) An IBM PC, XT or AT would require at least 4 expansion cards for similar hardware: one video graphics adapter card, one floppy disk controller (FDC) card, one serial and parallel port card, and one sound card with a joystick port. (A third-party multi-IO card might merge the ports and FDC onto one card.) Therefore, the 5 XT slots of the original Tandy 1000, 1000 TX, 1000 SX, and similar models remained available for other hardware, making them equivalent or better than the 8 slots in IBM’s XT and AT models (which had 8 slots because the original PC’s 5 proved inadequate.)

Tandy 1000

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The original Tandy 1000 was a large computer almost the size of the IBM PC, though with a plastic case over a steel lower chassis to reduce weight. The original Tandy 1000 featured a proprietary keyboard port (using an 8-pin DIN connector) along with 2 joystick ports (using 6-pin DIN connectors) on the front of the case. The rear featured a RGB monitor connector (a standard 9-pin female D-shell compatible with CGA/EGA monitors), an RCA-style composite video-out connector, a single RCA-style monophonic line-level audio connector, a light pen port, and an edge-card connector used to attach a parallel printer.

The printer port followed the old Centronics standard and was not fully compatible with the parallel port found on PCs. The original Tandy 1000 came standard with one internal 5.25” double density floppy disk drive, with an additional exposed internal bay usable for the installation of a second 5.25” disk drive (available as a kit from Radio Shack). The floppy drives used the old-fashioned method of selecting the drive number with jumpers instead of the IBM cable twist. 128k of memory was standard, with the computer accepting up to 640k of total memory with the addition of expansion cards. MS-DOS 2.11 and DeskMate 1.0 were included with the system.

The original Tandy 1000 (and many other models), like most home computers sold at the time, did not have a hard disk drive. The Tandy 1000 HD was essentially an original Tandy 1000 with a hard disk option factory installed. The factory hard disk had a capacity on the order of 10 or 20 MB.

  • Original Retail Price: $1,199
  • Base Configuration: 4.77MHz 8088 CPU; MS-DOS 2.11; three ISA slots; 128K RAM (640K max); 5.25-inch floppy disk drive; keyboard/keypad; parallel, game, and light-pen ports; DeskMate software; BASIC; three-voice sound
  • Video: 640 x 200 graphics, CGA
  • Important Options: internal or external 10MB hard disk drive, 10MB Bernoulli drive, monochrome VM-2 or color CM-2 CRT display, RS-232C interface, modem

Tandy 1000 EX

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The Tandy 1000 EX was designed as an entry-level IBM compatible personal computer. The EX was a compact computer that had the keyboard and 5.25" floppy drive built into the computer casing. The 5.25" drive was accessible from the side of the computer, on the right hand side. The EX was marketed as a starter system for people new to computing, and sold for $1000.00 from Radio Shack in December 1986. The EX and HX would be among the most popular of the Tandy 1000 line because of their low price.

The EX had a 4.77 MHz 8088 and one internal 5.25” floppy drive. An external drive could be connected to a port on the back.

Tandy 1000 HX

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The Tandy 1000 HX was the bigger brother of the EX. It was mostly the same machine, but had a 3.5" floppy instead of a 5.25" one, and also had DOS 2.11 in ROM, which could be accessed by starting the computer with no bootable disk present. A Tandy 1000 HX, with a Tandy RGB monitor, an external 5.25 disk drive, joystick, and a Tandy DMP-133 dot matrix printer.The computer's memory could be expanded to 640k. This would be accomplished by placing a memory expansion card, which came with 128k, in the expansion slot and adding another 256 (for a total of 384) kilobytes in memory chips to this board.

The cards were ISA, but used a pin rather than an edge connector. Called “Plus Cards”, the pin connectors allowed them to be smaller than standard ISA cards. Multiple Plus cards were stacked rather than connected to separate motherboard connectors, also saving space. Radio Shack eventually sold an adapter card that allowed the installation a of “Plus Card” into a standard ISA slot, such as those in the larger Tandy 1000 models. There were three card positions available in the computer case. In addition to the 5.25” drive bay of the EX model, there was another 3.5 inch drive bay in the computer case. On the back of the machine there was a port which allowed a user to connect an external 360k 5.25” or 720k 3.5” floppy disk drive unit, available from Tandy.

The 1000 HX did not come with a hard drive, and Tandy did not offer fixed disks for it. However a number of third party vendors made fixed disks for the HX available for sale. The design of the EX and HX did not make it easy to add a hard disk, however.

The settings on the computer could be changed so that instead of looking in ROM for DOS at bootup that it would go to the floppy drive instead. Most versions of MS-DOS worked with the 1000 HX, including DOS 3.x, and some later versions. There was a quirk in the DOS 4.0 environment that prevented that version of DOS from working with Tandy 1000 HX computers.

Tandy 1000 SX/TX

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The Tandy 1000 TX was very similar to the Tandy 1000, having an external keyboard and similar casing. The most major difference was the use of an 80286 CPU; otherwise, it was nearly identical to the Tandy 1000, including the unique parallel port edge connector. Despite the 80286 processor, it was still an XT-class PC, not an AT-class PC, as it adapted the 80286 to operate over the same 8-bit data bus as previous Tandy 1000 models, and had 8-bit XT-style expansion slots. As such, it could not operate in 80286 protected mode or perform 16-bit memory or I/O transfers in one bus cycle, but it did benefit from the higher speed of the 80286 and its other added instructions in real mode. The TX had a 3.5" internal floppy disk drive, with an optional additional internal 5.25" floppy disk drive. It contained ports for two joysticks in the front along with the keyboard, and included a volume control with a headphone jack on the front. The back had all of the same ports as the Tandy 1000, except that the light pen was replaced with a serial port. The memory size was 640k (upgradable to 768k, with the added 128K devoted to video*) and the computer came bundled with DeskMate.

The SX was the lower-end sibling of the TX. It used a 7.16 MHz 8088-2 processor, had 384k of memory (upgradeable to 640K on the motherboard,) came with either one or two 5.25” internal floppy disk drives, had the light pen port instead of the RS-232 serial port, and lacked the volume control and headphone jack. All original Tandy-provided internal floppy disk drives for the 1000 SX and TX were double-density drives.

  • Unlike the IBM PC, PC/XT, PC/AT, and all compatibles, the Tandy 1000 series (except for the VGA-equipped RLX and RSX) used part of main memory as video memory, as the IBM PCjr did. Expanding the TX’s memory to 768K ensured that more memory would be available in the 640K of the memory space allocated by IBM for main memory (for programs and their data).

Tandy 1000 SL, SL/2, TL, TL/2, TL/3

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The Tandy SL and TL series of computers were updates of the SX and TX respectively. Aside from having a redesigned case, the SL and TL each offered improved video hardware capable of 640x200x16 graphics, on-board Hercules Graphics Card compatible monochrome video offering 720x350 resolution, and an improved sound circuit featuring an 8-bit mono DAC/ADC. The composite output was also dropped. The latter device, which became known as the "Tandy DAC," was broadly similar in function to sound devices which connected to the parallel port (such as the Disney Sound Source), but unlike those devices it supported DMA transfers and could sample at frequencies up to 48 kHz. While the Tandy DAC's features compared favorably to those offered by Creative's 8-bit Sound Blaster audio cards, it never saw widespread adoption by software developers. The 640x200x16 graphics mode was rarely used either, as it was not supported by the BIOS. The TL line also allowed the onboard floppy controller, parallel port, and joystick ports to be disabled, which the earlier models did not.

The Tandy 1000 SL and SL/2 feature an Intel 8086 processor running at 8 MHz. The 8086’s 16-bit bus and slightly higher clock speed gives the SL models a small but definite performance advantage over the earlier 8088-based Tandy 1000s. The SL came with 384k of RAM preinstalled, whereas the SL/2 offered 512k. Both machines can be expanded to 640k, although only 576k could be used by the operating system.

The Tandy 1000 TL and TL/2 use 8 MHz Intel 80286 processors, whereas the TL/3 uses a 10 MHz 80286. These computers had 640 kilobytes of memory preinstalled, with an option for an extra 128 kilobytes to be installed for use as video memory for the onboard ETGA (Enhanced TGA, the “Enhanced” referring to the added 640x200x16 color mode) video hardware. It is therefore impractical to expand the onboard memory beyond 640 KB if a VGA graphics card is installed. Notably, the TL/3 had a high-density floppy controller for the first time, although it only shipped with a double-density 3.5” drive.

Since the TL series are XT-class machines, it is impossible to install or use extended memory (XMS), although expanded memory (EMS) can be used in conjunction with an 8-bit LIM EMS memory card for software that supports expanded memory.

The SL and TL were also shipped with MS-DOS 3.3 and DeskMate 3 in ROM, and featured an EEPROM memory chip to store BIOS settings (which enabled similar functionality to today’s CMOS NVRAMs, so that startup options could be saved). The machines could also run ‘normal’ MS-DOS 3.x, 5, and 6 and Windows 2 and 3.0, albeit in real mode. In common with many PC Clones of the era, MS-DOS 4 was problematic and generally avoided.

Tandy 1000 RL, RL/HD, RLX, RSX

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The Tandy 1000 RL/RLX/RSX series were slim-line desktop home computers. The RL and RL/HD featured a 9.56 MHz 8086 processor, 512 KB of RAM (expandable to 768 KB to provide 128 KB for video), smaller keyboard and mouse ports (which were similar to the PS/2's ports but not directly compatible), a bidirectional parallel port instead of the edge-connector ports, and the SL's enhanced graphics and sound. The RL/HD also included a built-in XT IDE hard drive.

The RLX was the ‘mid-range’ offering of the RL line. It had a 10 MHz 286, and unlike other 286-based Tandy 1000s, it supported extended memory. However, it was not a full AT-class machine, as it still had an 8-bit ISA bus and only 8 IRQs. While the 3-voice sound chip and DAC were still present, Tandy video was dropped. The RLX had VGA instead, but it only had 256k of video memory and was limited to 640x480x16 graphics. Also, the RLX featured a high-density, 1.44 MB 3.5” disk drive. The RLX offered 512KB of memory preinstalled, which could be expanded to 1 MB. (The hard disk version came with 1 MB preinstalled.)

The RSX offered a 25 MHz 80386SX processor, two 16-bit ISA slots, AcuMos SVGA video, an AT compatible IDE interface and standard PS/2 keyboard and mouse ports. It was a full 386-class PC, and could use up to 8MB of memory. On the other hand, the RSX still had the 3-voice sound chip.

The later Tandy 1000 systems (SL/TL/RL/RLX) and follow-ons were also marketed by Digital Equipment Corporation, as Tandy and DEC had a joint manufacturing agreement.

Tandy 2000

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* Original Retail Price: $2,750 to $4,250
* Base Configuration: 8MHz 80186 CPU; MS-DOS 2.0; four proprietary expansion slots; 128K RAM (768K max); 5.25-inch floppy disk drive; keyboard/keypad; RS-232C, parallel, and composite video ports; Microsoft BASIC
* Video: 640 x 400 graphics
* Size/Weight: 18.75 x 21.25 inches, 41 lbs.
* Important Options: second 5.25-inch floppy disk drive, 10MB hard disk drive, Disk Cartridge System, 12-inch monochrome VM-1 or 14-inch color CM-1 monitor, graphics upgrade, mouse, floor stand

The Tandy 2000 was a personal computer introduced by Radio Shack in late 1983 which used the 8 MHz Intel 80186 microprocessor. By comparison, the IBM PC XT (introduced in March 1983) used the older 4.7 MHz 8088 processor, and the IBM PC AT (introduced in 1984) would later use the newer 6 MHz Intel 80286. Due to the more efficient design of the 80186, the Tandy 2000 ran significantly faster than other PC compatibles on the market, and slightly faster than the PC AT. While touted as being compatible with the IBM XT, the Tandy 2000 was different enough that most software that was not purely text-oriented did not work properly. It differed by having a Tandy-specific video mode (640x400, but not related to or forward-compatible with the 1987 VGA standard), keyboard scan codes, and possible other differences.

Tandy 3000

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Announced in July 1986, the Tandy 3000 was the company’s first IBM PC AT compatible and one of the top sellers in its class. Like many other manufacturers, it competed with IBM on price and performance, using a faster 80286 processor. Units sold with hard drives were designated Tandy 3000HD. The 3000 HL replaced the Tandy 1200. Original Retail Price: $2,599 to $3,599 Base Configuration: 8MHz or 12MHz 80286 CPU, MS-DOS 3.1, 10 ISA slots (eight open), 512K RAM (1MB max), 5.25-inch floppy disk drive, keyboard/keypad, RS-232C and parallel ports, Professional DeskMate software, utilities disk, installation and operation manual Video: CGA Size/Weight: 6.5 x 19 x 18 inches, 42 lbs. Important Options: OS/2 or Xenix 5.0, 3.5-inch floppy disk drive, 20MB or 40MB hard disk drive, tape backup unit, 12-inch monochrome VM-1 or 14-inch color CM-1 monitor, EGA card, modem

Tandy 4000

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The new Tandy 4000 LX computer uses the high-speed 20 megahertz (MHz) Intel 80386 microprocessor and comes standard with 2 megabytes (Mb) of 80-nanosecond random access memory (RAM) utilizing highly-reliable, single in-line memory modules (SIMMs). Today's introduction offers customers a clear choice in 80386-based computers between the AT bus architecture on the 4000 LX and the IBM Micro Channel-type architecture used in the Tandy 5000 MC personal computer. The 4000 LX is designed to be expanded as the customer's needs grow, operating as a single-user PC running MS-DOS 3.3 or MS OS/2 operating systems, or as the engine of a multi-user system such SCO XENIX 386 operating system. The speed and expandability of the 4000 LX also make it an ideal file server in a 3Com or TandyLink connectivity environment.
Furthermore, the support of powerful video options, such as VGA, EGA and CGA, also make it an effective engineering workstation or desktop publishing system. Standard configuration of the 4000 LX includes a 3.5-inch, 1.44 megabyte (Mb) floppy disk drive, a socket for an optional 20MHz 80387 math coprocessor and eight expansion slots (six 16-bit and two 8-bit). The LX achieves maximum performance at zero wait states by using a memory management scheme that interleaves data between two banks of memory.

A 32-bit Tandy-designed memory expansion slot is also included for high- performance memory accesses. The optional memory expansion board allows for maximum memory configuration of 16Mb using 1Mb SIMMs or 8Mb using 256Kb SIMMs.

Two open 5.25-inch half-height drive slots and an optional non-accessible 3.5- inch drive slot allow the customer to choose from a wide range of storage options selecting the configuration which best meets the computing needs of the business. Tandy’s 5.25-inch storage device slots incorporate a new rail system so that installation of these drives is as easy as sliding them into a slot and connecting the ribbon cable.

Storage options include 3.5-inch, 720 kilobyte (Kb) or 1.44Mb floppy disk drives; 5.25-inch, 360Kb or 1.2Mb floppy disk drives; 20Mb, 65 millescond (ms); 40 Mb, 40ms; and 40Mb or 70Mb, 28ms standard hard disks as well as a 40Mb tape backup. Tandy has expanded its mass storage options this year to include five types of Small Computer Systems Interface (SCSI) devices: 40Mb or 80Mb, 19ms hard drives; 170Mb or 344Mb, 16ms hard drives; and a 150Mb tape backup.

The 4000 LX also incorporates a new, 101-key enhanced keyboard with tactile feedback, parallel port, asynchronous serial port, and keylock. Designed and manufactured by Tandy in Fort Worth, the 4000 LX follows the company’s tradition of innovative pricing with its suggested retail price of $3,999.

The Tandy 4000 personal computer, introduced in 1987, is a 16MHz 80386-based computer which has been enhanced to support an optional 16MHz 80387 coprocessor for processing math intensive applications with greater speed. With a suggested retail price of $2,599, the Tandy 4000 computer includes 1Mb of memory expandable to 16Mb.

  • 4000 HD 1987 - 1989 Intel 80386DX 16.0 MHz
  • 4016 DX 1989 - 1990 Intel 80386DX 16.0 MHz
  • 4000 SX 1989 - 1990 Intel 80386SX 16.0 MHz
  • 4016 SX 1989 - 1990 Intel 80386SX 16.0 MHz
  • 4020 SX 1989 - 1990 Intel 80386SX 20.0 MHz
  • 4000 LX 1988 - 1989 Intel 80386DX 20.0 MHz
  • 4020 LX 1990 - 1991 Intel 80386DX 20.0 MHz
  • 4025 LX 1991 - 1992 Intel 80386DX 25.0 MHz
  • 4033 LX 1991 - 1992 Intel 80386DX 33.0 MHz

Tandy 5000

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Operating at 20 megahertz (MHz), this Intel 80386-based desktop computer utilitizes a high-speed memory cache controller for superior speed and performance. Based on the latest in PC technology, the Tandy 5000 MC computer is a full-featured personal computer designed for more demanding business applications requiring the power of the 80386 microprocessor, video graphics array (VGA), high-speed memory caching and IBM Micro Channel-type architecture. In the 80386 computer market, Tandy customers now have a choice between the Tandy 5000 MC with the IBM Micro Channel-type bus and the Tandy 4000 computer with the industry-standard AT bus.
The Tandy 5000 MC has VGA capability on the main logic board that provides CGA, EGA, MCGA and VGA software compatibility. For customers needing extended VGA capabilities in the future, an IBM Micro Channel-compatible slot includes the required video extension features.

Operating enviornments for the 5000 MC range from the single-user MS-DOS 3.3 operating system to multi-user SCO XENIX 386 and multi-tasking Microsoft OS/2 operating systems.

The Tandy 5000 MC features the Intel 82385 memory cache controller with 32 kilobytes (kB) of static random access memory (SRAM). This allows the 5000 to achieve an effective zero wait state performance.

As with the Tandy 4000 personal computer, the 5000 MC utilizes state-of-the- art, highly-reliable single in-line memory modules (SIMM) for memory expansion. Standard configuration of the Tandy 5000 MC includes two megabytes (Mb) of dynamic RAM (DRAM) using 256 Kb SIMM devices. An additional 2 Mb can be added to a dedicated memory board using 256 memory devices. A maximum system memory of 16 Mb may be achieved using 1 Mb SIMMs.

The system has a total of five IBM Micro Channel-compatible expansion slots in addition to two 32-bit proprietary memory expansion slots. The dedicated memory slots allow memory transfers, which do not come from the cache memory, to occur at even faster rates.

Included with the base configuration is a 1.44 Mb, 3.5-inch floppy disk drive with room for three additional half-height storage devices. The front accessible device slots will accomodate an additional 3.5-inch and two 5.25- inch internal devices to allow customers to select the storage options which they prefer.

Other standard features include a socket for an optional 20 MHz 80387 math coprocessor, serial and parallel ports, dedicated mouse port, real-time battery backup clock, 101-key enhanced keyboard, and a key lock.

One of the standard configurations includes a super high-performance Micro Channel-type ST-506 hard drive controller and a 3.5inch, 15 millisecond 84 Mb hard drive, both designed specifically for the 5000 MC.

The controller card is the highest performance ST-506 disk controller available. It features full track buffering and read-ahead cache. It also maintains a one-to-one interleave factor while bursting data across the Micro Channel-type bus at 4 Mb per second. This high-speed performance meets the needs of the most demanding business applications such as computer-aided design, manufacturing and engineering as well as users who require large amounts of data manipulation and number crunching.

In keeping with Tandy’s philosophy of flexibility in options, mass storage devices include all three of the industry-standard interfaces - ST-506, ESDI and SCSI. All of Tandy’s current hard drives may be used with the system.

The Tandy 5000 MC computer is targeted to Fortune 1000 companies as well as small and medium-sized businesses which require multi-user and multi-tasking capabilities. Additionally, specific vertical markets will be addressed through Tandy’s Value-Added Reseller, Marketing Assistance Professional and Consultant Liason Programs.

The Tandy 5000 MC (Catalog number 25-6000) has a suggested retail price of $4,999 for the base system without a hard drive, and $6,499 for a 40 Mb hard drive version. The Tandy 5000 MC with the 84 Mb hard drive and ST-506 controller has a suggested retail price of $6,999.

See: "COMPANY NEWS; Digital Sets Plan to Build Its Own PC's" New York Times, 8 February 1982


External links

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2010-05-17 Computer, Hardware

Pre 1980 Micro-Computers

Here are some of the early systems (pre 1980) that “Got me interested..” prior to buying my first computer. (Radio Shack TRS-80 Model 1)


MOS Technology's first processor, the 6501, could be plugged into existing motherboards that used the Motorola 6800, allowing potential users (i.e. engineers and hobbyists) to get a development system up and running very easily using existing hardware. This enraged Motorola, who immediately sued, forcing MOS to pull the 6501 from the market. Changing the pin layout produced the "lawsuit-friendly" 6502. Otherwise identical to the 6501, it nevertheless had the disadvantage of having no machine in which new users could quickly start playing with the CPU. Chuck Peddle, leader of the 650x group at MOS (and former member of Motorola's 6800 team), designed the KIM-1 in order to fill this need. The KIM-1 came to market in 1976. While the machine was originally intended to be used by engineers, it quickly found a large audience with hobbyists. A complete system could be constructed for under 500 US$ with the purchase of the kit for only 245 US$, and then adding a used terminal and a cassette tape drive.
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Many books were available demonstrating small assembly language programs for the KIM, including “The First Book of KIM” by the legendary Jim Butterfield et al.

One demo program converted the KIM into a music box by toggling a software-controllable output bit connected to a small loudspeaker.

As the system became more popular one of the common additions was the Tiny BASIC programming language. This required an easy memory expansion; “all of the decoding for the first 4 K is provided right on the KIM board. All you need to provide is 4 K more of RAM chips and some buffers.” The hard part was loading the BASIC from cassette tape – a 15 minute ordeal.


Altair 8800

The MITS Altair 8800 was a microcomputer design from 1975 based on the Intel 8080 CPU and sold by mail order through advertisements in Popular Electronics, Radio-Electronics and other hobbyist magazines. The designers hoped to sell only a few hundred build-it-yourself kits to hobbyists, and were surprised when they sold thousands in the first month. The Altair also appealed to individuals and businesses who just wanted a computer and purchased the assembled version. Today the Altair is widely recognized as the spark that led to the microcomputer revolution of the next few years: The computer bus designed for the Altair was to become a de facto standard in the form of the S-100 bus, and the first programming language for the machine was Microsoft's founding product, Altair BASIC.
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The MEK6800D2 was a development board for the Motorola 6800 microprocessor, produced by Motorola in 1976. It featured a keyboard with hexadecimal keys and a LED display, but also featured an RS-232 asynchronous serial interface for a Teletype or other terminal. There was an on-board debug program called JBUG fitted in a 1k ROM, and the maximum RAM capacity on board was 512 bytes, but this could be expanded via the Motorola EXORciser computer bus interface. There was also a parallel bus interface for general purpose I/O. Another popular monitor program for this system is called MIKBUG.



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The Mini-Scamp was based on the SC/MP CPU from National Semiconductors. It boasted a massive 256 bytes of RAM - this was 4 times more than the earlier model. It had no ROM or EEPROM of any kind. The complete user interface consisted of 18 toggle switches, 2 pushbuttons and 9 LEDs. Binary code was entered into the RAM by dialing up the data byte and address in binary using toggle switches.

Pressing the deposit button stored the byte in memory. The LEDs showed the current contents of the memory location. After the program was entered in this manner one of the switches on the right was flipped from DMA to run mode and the code was executed. The micro could display bytes on the LEDs and read bytes from the data switches - the request LED was there to signal the user to enter a byte and press deposit.


Altair 680

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The diminutive Altair 680 was one of the first three Motorola 6800 computers on the market, along with the SWTPC 6800 and Sphere. Although the 680 was "pre-announced" on the cover of the November, 1975 issue of Popular Electronics (following the similar introduction of its big brother, the Altair 8800), the headline trumpeting "THE FIRST MOTOROLA 6800 COMPUTER PROJECT" was not the whole truth. Ironically, page 5 of the same magazine carried an ad for the Sphere, a 6800 based computer available in kit form for $860, and page 89 advertised the SWTPC 6800 kit at $450. It's hard to say which computer actually shipped first in quantity.

MITS offered a discount for orders placed before December 31, 1975, but the ads offering the discount featured a picture of the mockup 680 that appeared on the Popular Electronics cover (yes, the 680 was a mockup, just like the 8800 photo on the magazine cover the previous January). Also, the "December 31, 1975" discount ads appeared in Byte magazine as late as February 1976. The 680 is much smaller than the 8800, measuring only 11" by 11" by 4-3/4".


DREAM 6800

Dream 6800 was a “kit” computer. The design was originally published in ELECTRONICS Australia, May, 1979 starting on Page 83.


Talks directly to your TV and is programmed in a high-level language!

Are you one of the many people who have been turned off microprocessors and computers by all the complexity and never-ending jargon? Well, here is your chance to really start learning about the subject. This simple and easy to build computer costs around the $100 mark, yet talks directly to your TV without the need for a costly video terminal.

One of the other big features is the built-in cassette interface which means you can store your programs on any cassette recorder. And there isa whole raft of sample programs to get you started. All you have to do is punch them in via the hexidecimal keyboard. In no time you'll have the whole library of your own programs, easily accessable on cassettes.

So start reading now. We've even provided a comprehensive glossary to help you wade through all the jargon which is inevitable in this new and exciting field. The title of the computer is itself a bit of jargon: Dream 6800, which stands for "Domestic Recreational and Educational Adaptive Microcomputer.."

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Now we’ll let the designer, Michael Bauer, of the Division of Computing and Mathematics at Deakin University, tell his story…

Surprising as it may seem, there are very few co-called “hobby computers” which inexpensively satisfy the needs of recreational home computing. The choice is between an “evaluation kit” (eg, 6800-D2, KIM-1, Mini-Scamp etc) or a BASIC system with a CRT terminal, 8k memeory, etc. The latter will set you back a few hundred dollars, while the evaluation kit doesn’t give you enough capabilities. And besides, a hobby is supposed to be pleasurable, not give you headaches. There are much easier and less expensive ways to produce a headache, other than sitting up all night for days on end, hand assembling a ridiculous machine-code program to play “Lunar Lander” (with a 7-segment LED readout), or trying to write an animated video game in a high-level language like BASIC which wasn’t invented for that purpose in the first place for a terminal that only displays alphanumerics.

Here’s what the “Dream 6800” home video computer has to offer:-

  • Lower Cost: the parts should come to about $100
  • A more useful display: Chunky graphics output to your colour or B&W TV giving a 64 x 32 dot matrix display.
  • Better Software: As well as the usual operating-system or monitor (used for memory examine and deposit, tape load and dump, go to user program, etc), CHIPOS incorporates a high-level language interpreter, CHIP-8, which was specifially invented for video games, graphic displays, simulations, etc. Further, CHIPOS supports machine-language programs as well, for the applications where CHIP-8 is inadequate.
  • Wider Appeal: People not into electronics or computing will also find the Dream 6800 fascinating. Lots of TV games and other programs have already been written in CHIP-8, so you’ll be able to impress your “non-believer” friends right away. And you wont hear the old: “Oh yeah, but what does it do?” and similar phrases. This is a fun computer!
  • There are hundreds of applications: TV games; advertising displays; teaching young children elementary arithmetic; practising morse code; timing events in the kitchen; hex/binary (variable base) calculator; metric conversions; bar charts; simulations (like LIFE); data communications experiments; etc.

Educational institutions will find it highly motivational for introductory machine-level programming courses. It’s also a serious computer!

Hardware Specifications

  • Processor: Motorola M6800.
  • Clock: M6875 with 4.00 Mhz crystal.
  • RAM (On-card): 1K x 8 (2 x 2114) Off-card expansion to 32K.
  • ROM (CHIPOS) 1K x 8 (2708).
  • Display: 64 x 32 dot matrix; each dot is 4 TV lines square. Uses 256 bytes of RAM at loc. 0100 for refresh by DMA. Video output: 1Vpp @ 75 ohm.
  • Input/Output: One M6821 PIA controls:
    • Hex keypad (16 keys, Function and Reset.
    • Tape I/O: 300 Baud; 2400/1200Hz FSK; Out: 0.5Vpp; In: 300mV - 3Vpp.
    • RTC timer interupt: 50Hz (frame sync).
    • Audio Bleeper: 2400/1200Hz (8 ohm spkr).
    • Display/DMA enable-disable line.
    • Add extra PIA’s, ACIA’s, etc, without any additional logic.
    • Power requirements (worse case): +5V (1A), -5V (100mA), +12V (100mA).

Note: Power supply, keypad and TV RF modulator are off card extras.

Right about now the sceptics will be saying: “But there is only 1K of RAM and the video refresh buffer’s got to be in there somewhere, and a scratchpad, and a stack or two… good grief! there won’t be enough left for a program! In fact there are 640 bytes free. Thats either a damned long machine-code program to hand-assemble, or a 320 statement CHIP-8 program. Most users will find this more than adaquate. CHIP-8 is a lot more memory-efficient than BASIC, assuming the application is graphics orientated and does not require any heavy number-crunching, or text manipulations.

For experimenters, there are a few spare I/O lines on the PIA and the system bus in terminated on two 16-pin sockets allowing memory and I/O expansion.

Most hobby computer designers take advantage of the increase in sophistication and lower cost of hardware to produce a more powerful system for the same price as earlier designs. The DREAM-6800 philosophy is to retain the meek processor power and small memory size of past generations, but at a much reduced cost, and to more effectively utilise the available memory. This is not to imply that the ‘6800 lacks power’; it is a superlative 8-bit MPU in every respect.


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2010-02-01 Computer, Hardware

The interface that connects the hard disk to your computer may have changed over the years. Luckily, the proceedure required for attempted repair of a failed hard disk remains unchanged.

  • Low Level Format
  • Create Partition
  • Format

MFM, RLL, EISA, and SCSI hard disks were supplied from the factory WITHOUT being low level formatted. Installers/Users needed to use DEBUG to jump to a specified memory location. This would initiate the low level format routine that was contained withing a ROM on the hard disk controller.

IDE (RLL with a rewired interface) hard disks were mostly supplied with low level formatting software on the drive. Installers/Users needed to retain the software by copying it to a floppy disk as a first resort.

The IDE manufacturers software is nearly always prefered to earlier (aftermarket) low level formatters. Early generic software was unable to correctly initialize the “SMART” (error remap) capabilities of an IDE drive.

I like to think of a hard disk as being like a carpark:

  • The low level format: Surveying and staking out the area.
  • Partitioning: Laying the Ashfelt over the Surveyed area.
  • Top level Format: Marking out the lines for the cars to park in.

The Hard Disk Low Level Format Tool will low level format a hard drive erasing the whole disk surface in the process which has the result, that it is impossible to restore data afterwards.

It supports SATA, IDE, SCSI, USB, FIREWIRE and Big drives (LBA-48) and the most popular manufacturers Maxtor, Hitachi, Seagate, Samsung, Toshiba, Fujitsu, IBM, Quantum and Western Digital.


I had a 200 gig WD2000JB-00FUA0 full of data. I took the drive to a knowledgable? friend to retrieve some data. Under protest I had to leave the drive with him.

Looks like his bios wasnt compatible with the drive. (Older bios?) But instead of stopping right there so that he didnt loose my valuable data.

He allowed his PC to see the drive in the bios as only 130GB?? He then determined to run various disk manager programs on the drive. He also informed me that NTFS was “unreliable” so (somehow) he managed to “convert” it to FAT. (OMFG KILL ME NOW)

Anyway.. the drive was stuffed. The partitions weren’t accessable to XP. After many “plays” I gave up on the data. Tonight I decided to try and get the drive back into a usable state. Tried Linux distros. I couldnt get a linux to see it either.

In desperation I searched for a low level formatter on the net. (hoping that may sort it..) I ran the above program on it about an hour ago. After a large delay. The program started to spit many errors. (indicating the drive wasn’t functioning properly)

So I reset the PC. Went into XP Disk Management and OMG the drive was there now!! But still not able to use it. So I ran the program again and this time.. It seems to be formatting properly. (It’s about 5% in without an error.. So far) Wish me luck.. :)

I also tried the software on a Seagate 13 gig earlier tonight. It didnt seem to actually do anything. The existing partitions on the seagate certainly weren’t wiped out.

But I have a feeling that a CDROM I had as a slave on the same IDE cable.. may have been interfering. (Some drives either need to be jumpered to accomodate a slave properly.. and visa versa.. otherwise results could be compromised.

I’d suggest always running the drive to be low levelled, alone, on its own IDE cable. And thats exactly what I will do with the Seagate 13 gig when the (yawn) low level format on the 200 gig finishes.. (sometime later today.. the way its going now..)

Hope this info helps someone.

(ps: I couldn’t count how many times I have recovered drive previously using low level software. pps: In the old (386/486 days) some bios’s had low levelling software built in!)

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2010-01-26 Computer, Hardware

Before there was CompuServe

The Age: Feb 9th 1982

The Age: Sept 21st 1982

There was “The Source”.

My first employer looked at The Source, and saw that it was good, and set about creating a local equivalent. He called it The Australian Source, and it was the first project I ever got paid for programming on.

Reader’s Digest got wind of The Australian Source, and told my employer that if that’s what his service was called when it went live they’d sue his socks off. So he changed the name to The Australian Beginning. It started off doing rather less than what he said it would do, and went downhill from there.

The system was hosted on a Data General Eclipse minicomputer (called a “mainframe” in all the publicity material) and written in DG Business BASIC (not a compiled language). There was a rack of about a dozen 300 baud modems. The host-side developers always used in-house 9600 baud connections, and never actually used the system at 300 baud - and the result was a clunky nested menu structure whose pages took ages to repaint at 300. Even at 9600 bps, though, Business BASIC made the whole thing fairly sluggish.

We had our own terminal programs for Apple II and Tandy TRS-80 clients, featuring a file download protocol that I designed. We couldn’t use XMODEM because (a) neither the Apple nor the Tandy ran CP/M, meaning that XMODEM’s 128-byte rounding of file lengths was problematic and (b) the DG minicomputer’s modem I/O and BASIC string handling was not 8-bit clean and (c) what’s XMODEM?. Buried in the download protocol was a bit stuffing technique that would have worked more like uuencode if I’d ever seen uuencode. If I recall correctly, I actually wrote a bit of DG assembly code to deal with that encoding on the host side as well as doing the 6502 version on the Apple.

We had three or four people working on the client side, frantically adapting games from 100 BASIC Computer Games for Apple II and TRS-80 just so that there was actually something to download.

I was terribly proud of our do-nothing information service, and remember being quite miffed when the Microcomputer Club of Melbourne set up its own BBS with one competent guy working on the software rather than an enthusiastic but essentially clueless team, and made something ten times as useful with only the club membership fee to get access and no hourly charges.

I don’t believe The Australian Beginning ever made money. In that regard, it was ahead of its time. posted by flabdablet at 6:30 AM on July 4, 2009 [4 favorites]

Original Posting

Quote: March 1984: There is an Australian attempt at emulating The Source's capabilities, called "The Australian Beginning" (TAB, they call themselves). This is Melbourne-based, and has suffered a few problems in its short lifetime. It is quite good, though it is very limited compared to The Source. Its electronic mail facility is cheaper, but it has never caught on with the business community.

Tandy Computer Centre (Bourke Street Melb.)

I first heard of “The Australian Beginning” around 1985. I was working in the Bourke Street Computer Centre (There were 3 Tandy Computer Centres in Melbourne back then.) as a Training Instructor.

The previous TI had moved onto “The Australian Beginning” as a “programmer”.

Sometime later I got a phone call from him. He wondered if I would like to “visit” TAB and have a look at what they were doing there.

Of course (being a total nerd) I accepted immediately.

When I found the place. (Plush building.. Total professional setup) I was impressed.

The “computer room” was an almost dust free environment. With filtered air being forced out constantly.

I was amazed at the hardware. (Never having seen a Minicompter system with my own eyes before.. Except in Photos)

After giving me a tour of the place. I was presented with some very thick 15” printouts.

It’s at that point that I knew there was something funy going on.

I was asked if I had been “hacking” their system. Which I hadn’t. I was shown many printouts of “someone” who had been hacking their system.

Many times they tried to get me to admit that I was responsible for the hacking of their system.

But I wasn’t.. I didn’t even know their dialup number.

Obviously they were clutching at straws.

I was told that if I was the one who was responsible for hacking them. They would offer me a very highly paid job. Because whoever had been into their system knew it better than they did.

Unfortunately I never did find out who was responsible. I dont know if they ever found out who did it.

A year or so later I’d heard TAB has gone belly up.

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2007-10-21 Computer, Hardware

I wonder what Wiki says about Xenix?

I was wandering around.. I ended up on Wiki..

Hmm.. Ammendments needed..

Early Xenix Versions not mentioned in article

TRS-80 Models 12 (after hardware upgrade), 16a, 16b and Tandy Model 6000 were all capable of operating Xenix.

I worked in a Tandy Computer Centre around 1985. I took to Xenix in a big way and ended up collecting a few of the Tandy Xenix machines. I also ended up with a lot of manuals. (All gone now..) The TRS-80 Model 16a had 2 x 8” floppy drives and also could operate on up to 4 external hard disk units. TRS-80 Model 16b’s were single 8” floppy with a 15MB hard disk unit installed in place of the second floppy drive.

The first Xenix version I could ever find in operation was Version 7. (I ended up working in Tandy Australia’s Head Office - Specifically doing the support on these Xenix computers) I was involved in upgrading existing inhouse 16a Xenix systems from Version 7 to System III. System III shipped with later TRS-80 Model 16b’s and all Tandy Model 6000’s.

All Model 16a, 16b or 6000’s were Motorola 68000 CPU with Zilog Z80 operating as an I/O only co-processor. All models were supplied with 64 KB or RAM that could be upgraded to a maximum of 1 MB RAM.

All computers that operate under Xenix require that their RAM to be appropriate to the amount of users that they are trying to support.

16a’s were initially supplied with 512 KB of RAM. Later, 16a’s were supplied with and could be upgraded to 768 KB RAM. 16b’s were supplied with 512 KB RAM and could be upgraded to 1 MB RAM. Model 6000’s were supplied with 1 MB RAM.

Each memory card could be populated with 256 KB of RAM. So to achieve 1 MB RAM required 4 memory cards.

Upgrading the RAM was just a matter of setting a hardware jumper and slotting in the card into the card cage. (accessable from the rear of the unit via 2 thumscrews and a cover.)

16b’s were initially sold with the Version 7 Xenix software. But could be directly upgraded to System III Xenix software when it eventually became available.

TRS-80 Model 12

The TRS-80 Model 12 externally looked exactly the same as the TRS-80 Model 16b or Model 6000. The Model 12’s could be upgraded to Model 16b or Model 6000 spec for a fee.

I would say that all Tandy Model 6000’s (which were the last in the range) were sold with System III. Althought the earlier System 7 would operate on the 16b or 6000 hardware.

There were subtle hardware differences between the models. There were many ‘mandatory’ upgrades that needed to be performed on earlier 16a ‘cards’. (that may or may not have been performed.)

Version 7 was an early implimentation. Many expected ‘bells and whistles’ were missing or just plain ‘broken’ on the Version 7 Xenix. Modem settings were all for BELL modems and the Z80 control of the serial ports seemed to be broken in the Xenix Kernel.

Back then most ‘businesses’ had no intention of ever connecting their Tandy Xenix to a modem. So it was no big concern.

But as a support person who had responsibility to know all I could about this ‘Xenix’. I ended up connecting a modem to my ‘work’ Xenix and learning all I could after hours. (matchsticks anyone?)

Therefore System III Xenix seemed the better choice. Also the version 7 implimentation plain and simple had many more configuration issues out of the box.

The System III Xenix just had more bells and whistles. Of course development systems were available to both flavours of Xenix.

The source of both versions contained SCO and Microsoft ownership messages. So SCO and Microsoft were involved in Xenix pre System III.

I also had an early Tandy Xenix manual that described the proceedure for bootstrapping Xenix on a PDP11 from a tape backup unit. It was supplied as a guide with one of the early tandy units I picked up. That unit was running 8” winchester 8MB hard disks from memory. But the manual wasn’t relevant to use to boot with. It was more as a early system admin guide.

I think some of this needs to be mentioned. The earlier versions of Xenix were supplied on 8” floppy. No one mentioned Cromemco? When we were selling the TRS-80 Model 16a (for AU $10k basic system) the Cromemco was our nearest competitor in cost terms? —Preceding unsigned comment added by ‘lazerzap’(talk) 05:58, 21 October 2007 (UTC)

Yep.. Blame Me… Its all my fault..

The real? History of Unix

Its been a Unix day.. Found This… Is this the real history of Unix? Have things changed that much for the Unix System Admin since 1986?

From: (Peter E. Yee)


Subject: Reprinted without permission (but worth it)

Date: 26 Mar 86 10:00:06 PST (Wed)


By Alan Filipski

The UN*X brand operating system was writting by two computer science researchers in a closet in the attic of a famous research laboratory (The Labs) in the late 1960s. The authors had complete freedom to design an operating system according to their own wishes without management constraints. This was because everyone at The Labs, including the management, thought they were janitors who spent their time in the closet wringing out mops or something.

The first version of the UN*X brand operating system was a game that simulated the gravitational motion of all known planets and satellites of our solar system. Soon such things as a file system and user procedures were grafted onto it. It ran on a PDP-7 computer that someone had stored in the closet and forgotten about.

Images: Pictures from the Closet

Later the authors made the mistake of drawing attention to themselves by asking the management for a larger computer. At this, the management took the operating system and, supposing it to be something of use only to hippies (or closet hippies), sent it University of California at Berkeley.

It may be coincidental, but at the about the same time cases of a peculiar compulsive mental disorder known as Unirexia Nervosa were first noted in San Francisco, Calif. area. The symptoms of this disorder are the interjection of nonsense words such as grep, awk, runrun, and nohup by the victim into his or her speech; the misuse of ordinary words such as cat and lint; and the avoidance of the use of uppercase letters.

Advanced cases of Unirexia Nervosa have been found at many major universities throughout the U.S., where youths with pasty complexions and sunken eyes can be found late at night subsisting on diet pop, glaring fanatically at CRT’s, and mumbling about “one more bugs”. Since for the most part this malady has been confined to university students, it has not cause great public alarm. But recently there have been reports of regular people contracting the disease, even some who hold otherwise respectable positions in industry. The mode of transmission of Unirexia Nervosa is not known, but it is thought to have something to do with beards.

Members of the UN*X community have developed a novel and effective means of communication with each other. Suppose a user named Athol at Epizootic Systems in Cupertino, Calif., wishes to send an electronic mail message to his friend Elba at Perjorative Systems Inc. in Palo Alto, Calif. Although their computers do not communicate directly, they message may be passed via intermediate links. Athol would merely type:

mail ihnp4!allegra!ucbvax!seismo!decvax!cbosgd!ucbvax!pejor!elba

and then enter the text of his message. This electronic mail would appear at Elba’s terminal either within two days of the time it takes to propagate a telephone signal 73 times between the East and West Coasts of the U.S., whichever is greater.

Although many people think the word “UN*X” is an acronym (or even a homonym), the word actually originated in the following manner. When management in The Labs noticed the strange machine running in the closet, they stopped the first technical-looking type they saw in the hall and asked him what it was. As fate would have it, it was not a technical type at all but a member of a lost Australian aboriginal tribe who had been wandering the halls of The Lab for years without drawing attention. The fellow did not understand English and believed they were asking him to haul the computer away. He replied, “UN*X(tm),” which is aboriginal for “Not my job, man.” The rest is history.

The different versions of the UN*X brand operating system are numbered in a logical sequence: 5, 6, 7, 2, 2.9, 3, 4.0, III, 4.1, V, 4.2, V.2, and 4.3.

The C programming language is descended from the languages B and BCPL (short for Bucephalus, Alexander the Great’s horse). It is a highly structured language. The following structured program, for example, is well-known to all C language programmers, and prints a well-known message at the terminal (try it!):

  1. define TWENTYNINE 29
 int ll, L1, l0, h_1,q,h1,h;
		putchar (ll),L1==2?ll=' ':0){
	:L1==sizeof L1&&ll==' '
		L1==5?ll-=8:q&& &
	h_1;L1==sizeof ll+2?

Note the absence of goto statements in the program. Also note how the portability of the program is enhanced by judicious use of the C preprocessor and the sizeof operator. The dereferenced null pointer at the end is used to make sure the output is properly terminated.

The most commonly used UN*X interactive command language is known as the Bourne shell. (This shell was recently completely rewritten and is now available as the Bourne-again shell.) The shell provides a uniform syntax by which the user can interact with the operating system kernel and utility programs. The utility programs in turn accept a uniform syntax of command line arguments and options. Typical examples of utilities are the ar utility, which requires single-letter options that are lumped together in a specified order with an introductory minus sign, before the other arguments; and the find utility, which has multiletter options that cannot be lumped together, each of which must be preceded by a minus sign and which follow any other arguments.

Besides being used interactively, the shell itself may be used as a programming language. Although programs written in shell are slower than equivalent programs written in C, they are shorter and easier to read and debug. For example, to add 1 to a variable a in C one would have to write:

 a = a + 1; 
 a += 1; 
 or even: 

In shell, one need only write:

 a = `expr $a + 1` 

where it is essential to have spaces around the + sign to use the $ sign only before the righthand occurrence of the variable a, and to use the backward quote character instead of the common single quote. When UN*X brand operating system programmers want to develop an application quickly, they often use the shell because of this convenient syntax.

Security is a very important issue in the UN*X brand operating system world. The typical UN*X brand operating system source licensee is living in a fool’s paradise, little realizing that on the streets of every major city wander broken hackers who would kill for access to kernel source code. These people may be down on their luck, but they are not stupid. As you read these words, there are people who but for lack of a quarter would be whistling uucp protocols at 1200 baud to your modem from a downtown pay phone.

Therefore, the prudent administrator should be aware of common techniques used to breach UN*X brand operating system security. The most widely known and practiced attack on the security of the UN*X brand operating system is elegant in its simplicity. The perpetrator simply hangs around the system console until the operator leaves to get a drink or go to the bathroom. The intruder lunges for the console and types rm -rf / before anyone can pry his or her hands of the keyboard. Amateur efforts are characterized by typing in such things as ls or pwd. A skilled UN*X brand operating system security expert would laugh at such attempts.

The Trojan horse strategy is used in many attempts to defeat the security of a UN*X brand operating system installation. The following scenario is typical: The UN*X brand operating administrator arrives at work one afternoon and finds a new terminal outside the system security area. Since it is better than the current system console, he brings it in to the computer. After a few minutes of use, hordes of cockroaches come pouring out of the back of the terminal, driven out by the heat. The operator jumps up to stamp them out and the intruder has his will with the system.

How can this sort of damage be prevented? The greatest weakness of the UN*X brand operating system is the fact that the superuser root is so powerful. Therefore, an important principle is simple to minimize the use of root. An ingenious way of doing this is to first, without looking, set the root password of the system to some randomly generated string of character. Do not memorize or even look at this string. Now set up the /etc/inittab file with the run level 2 flag that will cause it to demand this unknown password whenever the system is booted. The system is now secure. Log off.

What can a system administrator do if he suspects that some has broken root? Simple. First, at the slightest suspicion that someone has unauthorized access to the superuser capability, immediately seal off the computer room, sound the fire alarm, release inert halon gas into the atmosphere, and activate the automatic sprinkler system. Type “shutdown 0” and cut all circuit breakers to the computer. Physically destroy all magnetic media that have ever been mounted on or associated with the insecure system in any way. Order a new distribution and reboot.

An administrator who is aware of these methods can maintain a sufficient degree of paranoia for most applications.

It has often been said that if God had a beard, he would be a UN*X programmer. While this may be an exaggeration, it is true that UN*X brand operating system is well on its way to replacing the outmoded 10- and 15-year-old operating systems in common use today.

Note: Remember article written 1986.. It’s been a long time coming..

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