TRS-80 "The Trash 80"

Page 1

Introduction to TRS-80

In the spring of 1977, I received a phone call from Ben Rosen, who at that time was a market analyst for Morgan Stanley. He was just about the only stock market analyst specializing in the infant personal computer industry and one of the industry experts. Ben, who later became the Chairman of both Compaq and Lotus, had already organized the first of his famous industry seminars, and he had invited me on a panel as a retailer. This call, however, was to tell me that I was about to receive a visit from an important person, if I had time to see and talk with him today. Ben went on to tell me that my visitor would be Charles Tandy, who owned the Radio Shack chain of some 7,000 stores. He had only that day, and he wanted to visit a successful computer store.

Mr. Tandy arrived shortly after lunch and introduced himself.

"Call me Charles," he said as I conducted him through my operation.

We started in the basement where we repaired computers, built many of them into systems, and had our stock room. Then to the selling floor, where he seemed most interested in the Apple II and the SOL. Charles was a man who could put anyone at ease, even if they knew how important a person he was. He had the knack of asking the most direct and revealing questions in a way that aroused no resentment. I really enjoyed talking with him, flattered that this powerful businessman would seek me out for advice. At the end of the day, he told me that he had visited other computer stores and in general classified them into two categories: first, stores run by computer hobbyists where a neophyte would be ignored, or snowed. The second type of store was run by ex-used car salesmen who were masters of the hard sell. They tried to completely snow the average prospective buyer. He said my store did not fit into either category (for which I was grateful,) but seemed to meet the customer at whatever level they were at. I told Charles that most of my salespeople were recruited from the hobbyist ranks, but that I had trained them somewhat in the art of retail selling.

We talked all afternoon, and at the end of the day he asked what I was doing that weekend, and would I consider going back with him to his headquarters in Fort Worth . It was common gossip in the industry that Radio Shack was going to be selling computers very soon, but nobody knew what kind they would be selling. Now it seemed that I was being invited to get an advance look. Of course I told Charles I would love to go with him.

The next morning was Friday, and I met the Tandy party in their suite at the Hotel Carlisle on Park Avenue for breakfast. After breakfast, we piled into a limo for a trip to the airport, but first we made a stop at a nearby shop where they sold novelty telephones. Charles bought a few as gifts for his friends back in Texas . Later I was told that he bought the store because they carried the most unusual phones. Phones packed aboard, we drove out to Teterbro Airport in New Jersey and boarded the Tandy corporate jet for the flight to Fort Worth .

All this was new and exciting to me. I had never flown in a corporate jet, and I had never been to Texas , either. Landing in Fort Worth , we all drove to a local barbecue which was Charles favorite, and then straight to the Tandy plant. There, Charles introduced me to most of his executives and told me they were developing a new type of computer for sale in their stores. He said that they had investigated all of the machines being offered for sale and had come to the conclusion that they were all too complicated and too expensive for the average person. They had therefore designed a completely new concept in small computers.

With that, they showed me what seemed to be a keyboard and a 12-inch TV screen, with a wire connecting the two units. The plastic case was colored with a metallic silver gray finish, and the keyboard and front of the TV was a contrasting black. The oversized logo on the front read "RADIO SHACK TRS-80" and "MICRO COMPUTER SYSTEM."

My first comment was, "Where's the computer?"

"It's inside the keyboard case," I was told.

"Right under the keyboard!" I could hardly believe it.

I was used to the Altair and Imsai_even the SWTPC 6800 and the SOL with their brute force power supplies and expandable bus. Even the Apple II, which I considered a masterpiece of compact design, took much more space than the TRS-80 keyboard unit. Then I noticed the external power supply plugged into the wall. Well, there was one reason for the size.

"We decided to use an external power supply to conserve space and keep the heat out of the computer case.

"Okay," I thought. That made sense.

I really liked the idea that the TRS-80 came with its own TV monitor. In those days video monitors were very hard to get and they were expensive. I had bought a huge order of 9-inch, high quality, security type video monitors to sell with my computers, and I sold them at a very small mark-up if the customer bought a computer.

Radio Shack had provided a 12-inch TV quality video display that was really a television with the radio section removed. This was a smart way to get a larger, reasonably priced video monitor if you had the buying power of Tandy.

"Tell me some more about the computer?" I asked.

"Well," someone answered, "it's a Z-80 based machine with 4K of RAM, and a ROM with the boot-up software and BASIC. Programs and data are loaded through a cassette. The video display has 64 characters and 16 lines and there are graphics characters as well as uppercase letters."

"This is interesting," I thought. "Just like the first Apple I."

"Tell me about the BASIC?" I asked.

"Well, it's out. Level I contained in a ROM. This is an integer-only version with only two character variables. Our Level II will be out shortly and will have enough advanced features for anybody."

By now I was very impressed with the TRS-80, and I fully realized that it was going to be hard competition for anything I sold, except possibly the Apple II. The big question in my mind was, how much would they sell it for?

As if he was reading my mind, Charles asked me, "How much do you think should I sell it for?"

I really had no basis of comparison except possibly the SOL (I had not received an Apple II yet,) and it sold for $1,400 with a video monitor. Well, this machine is a lot simpler, so I should figure about $1,000. However this is Radio Shack so it must be cheaper. I'll say $900.

"Well," I said, "about $900 would be a fair price."

"What would you think about $600?" one of the Tandy people answered.

"If you are going to sell this system with a video display and built-in BASIC for $600, you better build a hell of a lot of them," I returned.

"Stan, just how many do you think would be enough?" one of the Tandy people asked.

"Enough," I said, "would be about 50,000."

"You are out of your mind," answered one of Tandy's staff. "No one has ever built more than 5,000 of the same type of computer, and we are thinking 12,000."

"You have 7,000 stores," I returned. "If you have only one to show and one to sell, that's no way for a big company to do business."

"We don't think all of our stores can sell computers; it's a specialized business."

"True," I answered, "but this computer may change all that."

After this exchange, I sensed a division in the company. Charles and all the people he had brought on board to develop the TRS-80 were convinced that the TRS-80 would be a tremendous success and would change their business. The older electronics people whose thinking was fixed in the audio, radio, and hobby electronics business did not understand the fascination of the computer for even the most conservative business person.

Charles then showed me folders containing cassettes and manuals for all kinds of home and business software. There were accounting programs, home management programs, and educational programs. They were all going to sell for less than $30.

At this I smiled and said, "Keeping business records on a tape cassette program has not proved very practical. (I was being very kind!) You would be well advised to keep your programs very simple until you get a disk-based system."

They ignored me and changed the subject. "How many of these computers could you sell in your store?"

"I would start with 10 per week and end up selling 40 or 50 a week," I replied.

They obviously did not believe me, but they didn't challenge my statements.

The meeting broke up at that point, and I was taken to a hotel to freshen up for some Texas hospitality later that evening. The next day was Saturday, and about 9:30 I received a phone call that Mr. Tandy was tied up, and that I should have my breakfast. He would pick me up later.

About 10:30 , Charles picked me up at the hotel and took me to the yet uncompleted Tandy Center . He showed me the building and parking lot with its subway into the center. He told me that it would become a center of life in Fort Worth , and he wanted it to be his contribution to the city he loved.

Then Charles told me how he had started in business making leather hobby kits and selling them in his craft stores. How he had bought the failing Radio Shack company, which was a retail electronics distributor that had evolved from ham radio equipment. He had built Radio Shack into the world's largest electronic retailer and one of the largest distributors in the United States . He believed that the personal computer industry was going to become very important in the near future. He also said that most of the companies then in business would fall within a year of two. The reason, he said, was because they were so disorganized and had no idea how to manufacture and market their products. I was very impressed with Charles' statements because I had staked my future on the industry, and I had the same feelings about some of the companies I did business with.

After we left the construction of Tandy Center , we went to the temporary offices of the corporation where we resumed our meeting. There I was told that Charles wanted to buy my store and hire me to train managers for his computer stores. The purchase price offered was not very liberal, but I was assured that my employment contract would be very good. I told them I would take it up with my partners.

When I returned to New York , I consulted my wife, who actually owned the store, and her parents, who had supplied some of the starting capital.

They said. "Do what you think best."

My partner, Mike Alpert, said that as long as he got back his investment and some return, he would go along with anything I wanted to do. So the decision was mine alone to make. One thing bothered me about this sale, and I called to talk it over with Charles Tandy. When I started the store in 1976, I did not draw any salary for a full year. We lived on my wife's salary as a New York City school teacher. It had always been my intention to pay myself that back salary when the store income allowed it. Now, if I sold out, that year would be down the drain. I explained this to Charles and told him that all I wanted was $25,000 for that hard year. He could not see it and told me that I was getting my foot on a high rung of the ladder at Radio Shack. He told me that all of the men who stuck with him when he took over Radio Shack were now millionaires. This attitude turned me off to the deal, and I decided to turn it down. The TRS-80 became the most popular computer ever built, but Charles Tandy passed away a year later. Most of the people he brought in to develop the Model I computer were gone shortly after his death. John Ratliff, Charles Tandy's assistant, told me that I would have never made it at Radio Shack.



The development of Level II BASIC gave the TRS-80 its first real chance to make good on all the promises Radio Shack had been making to the public. This vastly improved language was able to be used for business and home applications. Most of the computers were Level II, but those who had bought the original Level I machines could have their machines upgraded for $120. Video games started to appear using the graphics characters, and the stock of available cassettes in all categories increased.

By 1978, semiconductor technology had advanced to the point where 16K memory chips had come down in price, and it was possible to offer an upgrade to the TRS-80. This removed the original memory chips and replaced them with new 16K RAM. Many users had this upgrade done when they had Level II BASIC installed. It was quite expensive to have Radio Shack make the upgrade and several small companies came out with do-it-yourself upgrade kits. These sold for about $140, about half the price of the Radio Shack installation, and many users bought the kits, opened their case for the first time, and installed their own RAM.

By 1976, Radio Shack was selling the Level II, 16K TRS-80 for $849. This included a numeric keypad, a 6K RAM, and the 12K ROM containing the Level II BASIC. The enhanced BASIC included such features as string handling, multi-dimensional arrays, and multi-letter variable names (Level I only had two letter variable names.) You could name cassette files, and full editing was supported. Since BASIC came in a 12K ROM, the entire 16K was available for user programs. In 1979, this was a huge amount of available memory. The TRS-80 was equal to a 28K system, and it was hard to imagine that anyone would ever need more than THAT!

The Expansion Unit and Disk Drives

The tape cassette had been considered a great improvement over paper tape for storing programs and data for personal computers, but soon it became apparent that it was not a satisfactory solution as a data storage medium. The serial transfer rate was too slow, and the method of converting digital data into audio frequencies for recording was subject to error. The inexpensive tape cassettes, designed for audio, were prone to failure and tape stretch that rendered them unreadable.

The S-100 computers were adopting floppy disk storage. Eight inch diskettes and the recently-invented 5 1/2-inch mini-floppies were coming into use. Apple Computer was selling their 5 1/2-inch disk drives for the Apple II as fast as they could make them.

For Radio Shack to develop a disk drive system, a major system unit had to be designed and manufactured. This was the Expansion Interface, a unit that could be mounted under the Video Display. It contained the RAM expansion_up to 32K could be installed. It also provided a real-time clock, serial interface, printer port, and, most importantly, the disk controller. The controller could support up to four floppy disk drives. The TRS-80 Mini Disk System used a diskette with a capacity of 83K formatted. The disk with the operating system on it had 53K remaining. There were 35 tracks per disk with 2500 bytes per track, divided into ten sectors. Data could be moved in or out of the disk at a rate of 12.5 Kbytes per second, a great improvement over tape cassettes. The operating system, TRSDOS, had to be on the first drive for the system to operate.

TRSDOS - the Radio Shack Operating System

The dominant disk operating system for 8080 and Z-80 CPU's was CP/M. It was used by almost all of the manufacturers of this type of computer, and therefore a considerable library of software had developed for CP/M systems. It was considered the standard for this type of computer.

Radio Shack chose to ignore the standard and develop their own operating system. It was more important for them to completely control their system than make a considerable stock of programs available to Radio Shack owners. In fact, Radio Shack made it impossible to run the standard CP/M on a TRS-80 computer by preempting certain entry points on the memory map. Since these points were in the system ROM, it was impossible to change them.

As a result, TRSDOS developed on its own. While it was possible to port many CP/M programs to TRSDOS, it was a task for an expert and required a rework of the program. In time, TRSDOS came to have as a big a library of software as CP/M and as much support among software publishers. There were several versions of TRSDOS, including some produced by third-party software developers, which were compatible, but included features not found in Radio Shack's versions. Eventually there were versions of CP/M that could be run on the TRS-80. These were not compatible with standard CP/M, and programs had to be specially configured to run on them.

The Model III TRS-80 System

At the end of 1979, there were over a million personal computers operating in the United States. In fact, it was possible that over a million TRS-80s alone were sold. Radio Shack has never released the figures. One result of this was a marked increase in television interference in homes. A computer in operation generates AC interference at radio frequencies. This can be broadcast through the air, or transmitted through the power lines.

It is the job of the FCC to regulate electronic equipment to see that these emissions do not interfere with communications. They have a massive job to do, and by 1978, a large number of complaints were being received. The FCC published regulations covering personal computers and expected the manufacturers to comply. Most of the computers at that time were housed in metal cabinets which shielded them and made it easy to comply with the FCC regulations. Two computers were housed in plastic cabinets and they could not meet the FCC Regulations. These were the Apple II and the TRS-80 Model I. Apple managed to gain approval by coating the inside of the cabinet with a metallic finish and shielding the cable openings.

Radio Shack, however, could not make the TRS-80 Model I meet FCC regulations because of the separate units and the cable connections between them. As a result, they accomplished a complete redesign of the TRS-80 into a completely self-enclosed desk top cabinet. This was called the TRS-80 Model III. First ready in July 1980, in its cassette version it sold for $699 and incorporated many features that had been included in the Expansion Interface. The Model III had a 12-inch screen, which displayed the standard 96-character ASCII set with both upper and lower case characters. It also displayed 64 graphics characters and 160 special TRS-80 characters. The keyboard provided for entry of all the standard characters, including upper and lower case. There was also a 12-key numeric keypad. The Model III used the Z-80 CPU and from 16K to 48K of RAM. A parallel printer port was provided. Data storage was provided by either cassette or an optional floppy disk controller, and up to two internally mounted floppy disk drives. Additionally, two external floppy disk drives could be connected into the system. There was an option for installation of an RS-232C port for connection to a modem.

Model III BASIC and MODEL III TRSDOS were improved over Model I, but care was taken to make Mode III software compatible with Model I. If this proved impossible, conversion programs were often provided.

The TRS-80 Model III was one of the most successful computers ever built. It was used in schools throughout the United States, replacing the failing Commodores. It was used in offices, factories, and homes. By 1983, when it was replaced by the Model 4, a couple of million must have been sold. (Radio Shack has never given out the figures.) It was supported by the largest software libraries in existence up to that time, and several other operating systems were written for it. It became the standard grade school computer in thousands of school districts and the mainstay of small business.

TRS-80 Model 4

The TRS-80 Model 4 was the best of the mark and included many improvements that should have been made to the Model III during its years of manufacture. The Model 4 was probably the best 8-bit, Z-80 computer ever built. Unfortunately it came out too late, and had to compete with the IBM PC/XT and the onslaught of the clones. It remained in the catalog for a long time as a replacement for Model III's in schools and offices where they did not wish to lose their investment in software.

The most striking thing about the Model 4 was its white color. Charles Tandy had selected the metallic silver and gray colors, and after he died nobody in the company wanted to change it. To the outside world it looked old-fashioned and brought to mind the "Trash-80" image that competitors had tagged the TRS-80 with. Finally, they caught up with the times and made the necessary changes.

For the first time, the TRS-80 had an 80-column by 24-line screen, with an option to display high resolution graphics. The memory was expanded to 64K with an option to increase it to 128K. The disk drives were double density (184K,) and the keyboard was a full function with three programmable function keys. The operating system for the Model 4 was TRSDOS 6, which had been developed from LDOS, one of the independent operating systems. In addition, for the first time, standard CP/M was available for use on The TRS-80. Microsoft BASIC 2.0 was provided as the main language.

The Model 4 was designed to be compatible with the Model III. However, when operating with Model III software, the video display was 64-characters by 16-lines and the 48K memory restriction applied. The Z-80, which operated at 4 MHz as a Model 4, only ran at 2 MHz in Model III mode.

Radio Shack also introduced a portable version of the Model 4 called the Model 4P. This had a 9-inch CRT and two disk drives in a portable case.


The TRS Model 100

The little TRS Model 100 was one of the most important computers in the history of the industry. It was the first truly practical, portable laptop computer, and it became the prototype for an entire industry. It was just as important as the Altair, or the IBM PC. (However, the Epson HX-20 came out before it. But it had too small a screen, because the technology of that time could not make a bigger screen for a low price.)

The Model 100 was 11 5/8-inches wide by 8-inches deep by 2-inches wide and weighed only a few pounds. It had a full keyboard that was easy to type on but was very noisy. The display was 8 lines by 40 characters, which was enough to see your text, and it had a built-in 300-baud modem.

The memory was expandable from 8K to 32K, and it only used four AA cells for power, or an AC adapter. The Basic was built in, and it included a serial port, a parallel printer port, and an interface connector for a bar-code reader. The prices ran for $800 to $1300, depending upon the memory. Later, a disk drive was developed for the Model 100, but most users typed on their laptop, and they dumped the data into their PC or MAC when they got back to the office using Lap Link software. This machine spread like wildfire among members of the press, and I can remember going to a press conference in 1984 where the speaker had to ask the reporters to stop clicking their Model 100's because the speaker could not be heard. In 1985, I went to a Space Shuttle launch, and in the press room almost every reporter had a Model 100 connected by telephone to the office.


An Evaluation of the TRS-80 Computers.

The TRS-80 family of computers has never received the credit they deserved as a cornerstone of the personal computer era. Mainly this is the fault of the Tandy Corporation, who failed to understand the importance of public relations in the development of a booming industry. While more TRS-80 computers were built and sold than any other kind, all the attention went to Apple, IBM, and even the small CP/M based machines, which never came close to TRS-80 in popularity and customer satisfaction.

Perhaps much of this was due to Tandy/Radio Shack's position as both manufacturer and retailer. They did not have to fight for shelf space in stores and woo the value-addled resellers. In addition, much of the TRS-80 sales went to schools and small businesses in the hinterlands of the U.S.A.

Not many major corporations were willing to trust their data processing to a "Trash-80" built by Radio Shack, no matter how good the technical people said it was. It was only when IBM made personal computers "respectable" did the data processing departments admit that there might be some value in these little computers.


Radio Shack TRS-80
(Model I)
Catalog: 26-1001
Released: August 1977
Price: US $599.95 (with monitor)
How Many: 200,000 (1977-1981)
CPU: Zilog Z-80A, 1.77 MHz
RAM: 4K, 16K max*
Ports: Cassette I/O, video,
Expansion connector*
Display: 12-inch monochrome monitor
64 X 16 text
Expansion: External Expansion Interface*
Storage: Cassette storage*
* Additional capabilties with Expansion Interface

RS=Radio Shack
80=Z-80 microprocessor

Where's the computer? It's in the keyboard! As one of the first home computers ever, the TRS-80 was a great success. Tandy wasn't expecting many sales, but this, their first computer, sold 10,000 units in the first month alone. It includes everything you need to have a real computer of your very own - the computer, monitor and cassette deck for loading and saving data.

Yes, these were the days when you bought, loaded and saved your data and programs on cassette tapes.

Floppy disk drives didn't come into common use until years later. Even then, they were very expensive, costing hundreds of dollars.

The TRS-80 Mini-Disk was available within a year of the TRS-80 microcomputer's release, but it cost $499, more than the computer itself.

Even three years later, in 1980, the TRS-80 floppy drive still costs about $425.

There aren't any internal expansion capabilities, but two versions were eventually released:
  • The first TRS-80 computers had no numeric keypad, and Level I BASIC with 4K RAM.
  • Later systems had an improved level II BASIC with 16K RAM, and a numeric keypad.

    The Level I to Level II upgrade includes attaching extra chips and wires to the motherboard - not for the amateur. Originally, Radio Shack would install the upgrade (after you purchased it) in your TRS-80 "at no extra cost to you!".

    Most serious users eventually purchased the $299 Expansion Interface, a well-designed and attractive external module which sits under the monitor.

    It offers many improvements over the basic TRS-80:
  • Printer port
  • Expansion port
  • Optional serial port
  • Up to 32K additional RAM
  • Two tape drive connectors
  • Signals for a real time clock
  • Floppy disk controller, up to 4 drives

    It isn't perfect, though. The cheap and unreliable connection between the keyboard and the expansion interface often causes system crashes and lock-ups. One fix is to solder the connection, making it permanent and impossible to seperate the two.

    Is the TRS-80 a portable computer? Well, not really, but you CAN purchase official carrying cases from Radio Shack!

    1978 Order Worksheet for the TRS-80 and Peripherals

     4K Level-I
     26-1003  16K Level-I 690.00
     26-1004  4K Level-II 499.00
     26-1006  16K Level-II 789.00
     26-1201  12" Video Display 199.00
     14-841 * Realistic CTR-41 Cassette Recorder 49.95
     26-2101 * Level-I User's Manual

    * Recorder and manual included free
     when computer is ordered with display
     16K Memory (RAM)
     26-1120  Level-II BASIC (ROM)

     These two options are installed by
     Radio Shack at no extra installation cost
     TRS-80 Expansion Interface
     26-1150 * TRS-80 Line Printer 1299.00
     26-1151  TRS-80 Screen Printer 599.00
     26-1160 * TRS-80 Mini-Disk (Requires 16K)

    * Requires Level-II BASIC, and
     Expansion Interface
     Payroll (up to 12 employees)
     26-1502  In-Memory Information 19.95
     26-1601  Home Recipe 4.95
     26-1602  Personal Finance 14.95
     26-1701  Math I 19.95
     26-1702  Algebra I 19.95
     26-1703  Statistical Analysis 29.95
     26-1801  Backgammon/Blackjack 4.95
     26-1802  Quick Watson! 4.95
     26-2001  T-BUG 14.95
     26-2002  Editor/Assembler 29.95
     26-2003  Level-I BASIC Course 12.95

    By 1980, Radio Shack had released the new TRS-80 Model III. It is basically a super-Model I, with all of the Model I options built-in, including up to 48K RAM and two (optional) internal floppy drives.

    There was some controversy with this announcement, though.
    From the official "Radio Shack TRS-80 Microcomputer NEWS" newsletters:
    September 1980: "First of all the Model I is not dropped, it is in the 1981 Radio Shack Annual catalog and the price is unchanged."
    Then, just 4 months later:
    January 1981: "During November we had our annual shareholders meeting and it was announced that manufacturing of the Model I computer would stop prior to the end of 1980. meet the new FCC regulations we would have to redesign the entire product, case and all."

    The Model I failed the new FCC regulations about RF emissions generated by computers. It is unshielded and could cause interference on near-by radios and televisions.

    Radio Shack TRS-80 Model II
    Catalog: 26-4002
    Announced: May 1979
    Released: October 1979
    Price: $3450 (32K RAM)
    $3899 (64K RAM)
    CPU: Zilog Z-80A, 4 MHz
    RAM: 32K, 64K
    Ports: Two serial ports
    One parallel port
    Display: Built-in 12" monochrome monitor
    40 X 24 or 80 X 24 text.
    Storage: One 500K 8-inch built-in floppy drive.
    External Expansion w/ 3 floppy bays.

    The TRS-80 Model II microcomputer system, designed and manufactured by Radio Shack in Fort Worth, TX, was not intended to replace or obsolete the Model I, it was designed to take up where the Model I left off - a machine with increased capacity and speed in every respect, targeted directly at the small-business application market.

    The Model II contains a single-sided full-height Shugart 8-inch floppy drive, which holds 500K bytes of data, compared to only 87K bytes on the 5-1/4 inch drives of the Model I.

    From the Operators Manual:

    Because of a special high-density recording technique, each diskette can contain 509,184 bytes of information, which is more than 5 times the capacity of a 5-1/4" diskette. (It would take a 70 wpm typist 24 hours of typing at speed to fill an 8" diskette.)

    Also available is the matching computer desk and a high-performance line-printer. The desk includes a pull-out storage drawer, and the Disk Expansion Unit with space for three additional 8-inch floppy drives.

    The cost:
  • Desk - $350
  • Computer - $3450 (32K RAM) - $3899 (64K RAM)
  • Disk Expansion - $1150 (1 disk drive) - $2350 (3 disk drives)
  • Line Printer III - $1999

    Inside the computer cabinet, it's a different world. There is no motherboard, all of the logic circuitry are on circuit boards in a card-cage with a passive backplane.

    There are four cards installed:
  • Processor card with the 4 MHz Z-80A CPU,
  • Memory card with 64K RAM,
  • Floppy Disk Controller card,
  • Video Display card.
    There are four open slots for future expansion. Other cards available include a hard disk controller, an arcnet network card, a graphics card, and a 6 MHz 68000 board set with extra memory (up to 512K) that can run XENIX.

    On the outside, there are two serial ports, one parallel port, and a connection for the external disk drives.

    Tandy had a great deal of software for the Model II, but there was not much support for the system from anyone other than Tandy.

    Radio Shack TRS-80 Model III
    Introduced: July 1980
    Price: US $699 base model
    US $2495 w/ 32K, dual drives.
    CPU: Zilog Z-80, 2.03 MHz
    RAM: 4K, 48K max.
    Ports: Cassette tape, expansion, serial
    Display: 12-inch B/W monitor: 64 X 16 text
    Strorage: 0, 1, or 2 internal 178K floppy drives
    External cassette @ 500 / 1500 baud
    OS: BASIC in ROM, TRS-DOS on disk

    The Model III is basically an upgrade of the Model I, which was released three years earlier. It has the same CPU, but it is faster, has more memory, and the floppy drives hold twice as much data, although the Model I could be upgraded to some of these features.

    But the major reason for developing the Model III was because the FCC had just instituted new regulations about RF emissions generated by computers and other electronic devices. The Model I was completely unshielded and was unable to pass the emission restrictions.

    The Model III system is entirely self-contained. The original Model I had edge-type connectors with ribbon cable connecting the keyboard to the (optional) Expansion Interface, as well as the floppy drives. This type of connection is very unreliable, and led to the occasional system crash or lock-up.

    Related Links

  • TRS-80 Model I from Ira Goldklang's TRS-80 Revived Pages
  • TRS-80 Model I from
  • TRS-80 Home Page
  • Tandy Catalog Numbers for Computers, Peripherals, and Software from Tim Mann's TRS-80 Page
  • A. Richard Miller's TRS-80

  • History of the Radio Shack Computers

    • 1921: - Radio Shack begins as a one-store retail and mail-order company catering to ham operators and electronics buffs.
    • 1963: - Charles Tandy buys the chain of stores, and within two years turned a $4 million dollar loss into a $20 million dollar profit.
    • 1977: August - Radio Shack announces the TRS-80 Model I microcomputer.
    • 1977: September - One month after launching the TRS-80, 10,000 are sold.
    • 1979: May - Tandy/Radio Shack announces the TRS-80 Model II.
    • 1979: October - Radio Shack begins shipping the TRS-80 Model II to users.
    • 1980: July - Radio Shack introduces the TRS-80 Model III, priced from US$700 to US$2500.
    • 1980: July - Radio Shack introduces the TRS-80 Color Computer, and sells for US$400.
    • 1980: July - Radio Shack introduces the TRS-80 Pocket Computer. Price is US$230.
    • 1981: January - Radio Shack ceases production of the TRS-80 Model I, and recalls units from the US market, due to failure to meet new FCC radio-frequency interference regulations.
    • 1982: January - Radio Shack introduces the TRS-80 Model 16, with 8-inch floppy drives, and optional 8-MB hard drive.
    • 1982: January - Radio Shack introduces the TRS-80 Pocket Computer, Model PC-2, for US$280.
    • 1983: March - Radio Shack announces its TRS-80 Model 100 portable computer. Price is US$799 for 8KB version, to US$1134 for the 32KB version.
    • 1983: May - Radio Shack introduces the TRS-80 Model 4, for US$2000.
    • 1983: October - Tandy/Radio Shack announces the "transportable" TRS-80 Model 4P, for US$1800.
    • 1983: Radio Shack introduces the TRS-80 Pocket Computer, Model PC-4, replacing the PC-1, for US$70.
    • 1983: Tandy releases the TRS-80 Model 2000, which uses the Intel 80186 microprocessor.
    • 1983: Radio Shack unveils the TRS-80 Model 12 at the CP/M '83 Show. Price is US$3200.
    • 1985: March - Radio Shack introduces the Tandy 6000 multiuser system. It features Z80A and 68000 processors, 512 KB RAM, 80x24 text, graphics, 1.2-MB 8-inch disk, optional 15 MB hard drive, TRS-DOS, or XENIX 3.0. It supports up to 9 users.
      Source: Chronology of Events in the History of Microcomputers