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T > TANDY RADIO SHACK  > TRS 80 MODEL I


Tandy Radio Shack
TRS 80 MODEL I

Credit for the TRS-80 invention is traditionally given to Don French and Steve Leininger. However, Ray Holt, Founder and Executive Vice-President of Microcomputer Associates, says that's not entirely true. He says his company was asked to build a prototype. Once this prototype was shown in early 1977 to Tandy president Lew Kornfeld, it was kept by Tandy for a short time. Leininger's team then reverse-engineered the motherboard and never admitted it. Holt also said he doesn't remember French.
About this controversy, Don French sent us this explanation:

It is odd that Mr. Holt does not recognize my name. As is well known, I am the "Father of the TRS-80", the project was my idea in the first place.
What the TRS-80 was including the serial bus was based on my requirements. One thing I required was a way to expand the system that would allow users to do so without opening the case, as that would cause a warranty issue. Steve did the hardware and software design based upon my requirements. I would be very surprised if any work was done without my knowledge. There were very few in the company who knew anything about the project until it was demonstrated to Mr. Tandy. In fact there was no-one in the company other than me who could interview Steve be sure he had the proper knowledge to take my concept and design the actual product. Originally Radio Shack was against the computer idea but I kept pushing for it. Finally, I convinced John Roach to visit the West Coast Computer Fair in 1976, he was amazed that people would line up for hours just to get in to the show. He came back and discussed the issue with Charles Tandy, who decided that we should at least look at the concept and see what we could do. On another visit to California, John met Steve Leininger at National Semiconductor and later at the Byte Shop. Steve was brought into Fort Worth not long after that for a Saturday interview. After spending the Saturday with him, I recommended that we hire him. He started shortly there after in a "skunk works" project in an old automobile showroom, next door to the RS offices, to take my concept and create the actual hardware and software.

After a short while a wire wrap system was built based upon the Z80 chip. We put Lei Chen Wang's (sp) tiny integer basic on an EPROM and I wrote a simple 1040 tax form. A meeting was called for the RS Executive Team. Mr. Tandy came in with his big cigar and sat down at the keyboard to use the 1040 program. He promptly put in a salary of $100,000 which caused the program to crash, as it was only integer basic at the time. I told him "to take a pay cut for now and put in something less that $32,000" and that we would be using a different math package that would allow larger numbers. He did and the program went through to completion. After the demonstration, Kornfeld, Tandy, Appel, Roach, Steve, and I sat around the conference table discussing how many we could sell. Steve and I both said 50,000 plus and every one laughed. We were told "we can't sell 50,000 of anything". It was decided that we would make 1,000 systems. The product was approved. In January 1977, after a meeting between Appel, Roach, Kornfeld, and Tandy, it was decided to produce a total of 3,500 since we had that many stores and in Kornfield's words 'when the product fails, we will use it in the stores for inventory control". He never thought we could sell any. He was just doing it to show that RS could be a technical leader.

That number was used as the production number up through the introduction on August 3rd. When I got back after the introduction and the Boston computer show, I had over 15,000 phone messages from people who wanted to order systems. It took RS months to catch up with production.

I left RS after Charles Tandy died and Kornfeld refused to honor a promise Charles had made to me because he recognized that the TRS-80 saved RS since its introduction coincided with the fall in sales of CB products. 

Mr. Holt had nothing to do with the development of the TRS-80 in any way. There are several discrepancies between what he said and what is true. For one, his was based upon the Jolt chip not the Z80 as the TRS-80 was. The Jolt was never considered in anyway as a viable processor for the TRS-80. We actually did a version based on the 8080 but switched to the Z80 when Zilog gave me a better price than Intel. Also, Mr. Holt's production numbers and time frames do not match the actual numbers and time frame of the project. The product was started in early 1976 and the design was complete by mid 1976 when we demonstrated the wire wrapped system to Mr. Tandy and the rest of the executive team. 

Since I was the product manager for computers since before the product existed, any discussion with third parties would have gone through me. 

Thanks to John Ward for the following detailed information :

VIDEO MODES
The TRS-80 Model 1 had 1KB (1024 bytes) of video RAM. The standard screen display was 64 characters wide x 16 down, which is 1024 characters in total (that is why there was 1KB of video ram).

The video RAM was separate from the RAM for programs - the video RAM was in the gap between the end of the ROM and the start of the actual RAM.

There was also a special double width display mode which had 32 characters wide and 16 down. Changing from standard to double width resulted in losing every other character horizontally - changing from double to standard resulted in a space between every character.

Each character position on the screen was a grid of 6 blocks. (2 blocks across, 3 blocks down.) Text was placed in the upper two rows by a separate controller chip, with the lower row being empty so that there was a space between text lines. This allowed very good quality text to be displayed, as the patterns for each letter were stored permanently in ROM. Graphics mode shared the same 2x3 blocks, and you could set each block on or off either individually by use of the BASIC graphics commands, or as a whole block of 6 by writing data directly to the video memory.

The text letters were very good quality, and were upper case only. An upgrade was available which provided lower case letters (this was a chip fitted inside, and a software patch loaded from cassette).

Each character position could contain text OR graphics - not both at the same time.

The graphics resolution was 128 pixels across, and 48 pixels down. (2 pixels for each character across, 3 for each character down). Each block was either 'on' or 'off' - there were no greyscales or colour. The pixels were rectangular, being slightly taller than they were wide.

INTERFACES
The base unit only had connections for power, monitor and cassette recorder. An expansion bus was provided later which connected to the separate expansion unit. This provided connections for disk drives, printers and other items.

STORAGE
The base unit had a single cassette interface which used audio cassettes for loading and saving programs. The volume setting on the cassette player was critical to loading, and changing the volume even a small amount usually resulted in the program not loading at all.

SOUND
The base unit had no sound capability. However, some very basic sounds could be created by using the cassette interface together with machine code software routines. An external amplifier needed to be connected to the cassette output to hear the sound.

DISPLAY
The original display supplied with USA models was a black and white RCA television without the tuner. Later models (in the UK and Australia at least) were supplied with a somewhat better quality green display monitor.

TRIVIA
There were at least 2 different types made - one had the numeric keypad separately (as in the photo you have), and another one which didn't have the keypad. There was then a name plate where the keypad would be, with TRS-80 written on it.

The computer got fairly hot at the back during use - there was a large heatsink there. The separate power supply also got rather hot during use.

The computer also gave off a large amount of radio interference, which made listening to the radio in the same room almost impossible.

The only switches on the unit apart from the keyboard were the on/off button next to the power cable, and a reset button next to the expansion bus. The reset button stopped the program running on the base unit, but didn't clear the memory (soft reset). With the expansion interface connected, the reset button also erased the memory (hard reset).

The Level II BASIC was actually very good compared to other machines at the time, and had a fairly large set of functions and features. Programs were typed in, and errors were only checked when the program was executed. Editing of program code could be done one line at a time, with a primitive line editor. All errors were displayed as a 2 letter code - eg. ?SN ERROR was Syntax Error.

Machine code was loaded into a reserved area of memory, and executed using a function call from BASIC. The specific area of memory to reserve had to be specified when the machine was first switched on (the opening screen was MEM SIZE? and you either entered a number to reserve memory, or just pressed Enter if this was not required.)

Machine code could also be loaded and executed from tape using the SYSTEM command.

Michael J. Davern reports :
While it recognized lower case characters, the display roms could only generate uppercase characters ... although you could get a third party hardware modifications that could allow the display of lower case characters (although with no descenders, i.e., letters like y, g, etc. did sat entirely above the line ... their tails did not descend below the line ... this was also true for the dot matrix printers available at the time (Tandy also had a thermal printer that you could buy ... but the paper was very expensive). Additionally you could get a third-party hardware kit to double the CPU clock speed (The one I had also changed the power on light to green to indicate it was operating in double speed mode)

Software could be saved to a conventional cassette tape record at a speed of 500 baud (1000 baud if you had the CPU clock speed double, but not always reliable). Interestingly, by reconfiguring how you connected the cassette player to the computer, games were able to produce sound, and in one game I recall some rather primitive voice synthesis (the game was called Robot Attack). Tandy also had an external add-on Speech Synthesis unit ... we had one on loan once).

Looking back now, probably the most intriguing software enhancement you could get was an extension to the Rom-based basic language. This software called "level 3 Basic" provide quite advanced graphics features ... including line plotting and the ability to create graphic "sprites". The most interesting thing about the software was who made it ... I distinctly remember the label saying "Microsoft". If this is the same "Microsoft" we know today, then this is probably the most useful and bug free piece of "state-of-the-art" software Microsoft developed.

The expansion interface unit included space for the power supplies for housing both main unit and the expansion unit ... unfortunately the Australian power supplies were of different manufacture and did not fit ... they also produced sizable magnetic fields ... enough to warp screen images if placed to close to the monitor, and to easily wipe magnetic media (ouch!).

Tim Hill reports:
One interesting note about the display of lower-case is that all the circuitry was in place in most all units, but was not enabled. The character-generator ROM used by Radio Shack had full upper and lower-case characters, but RS did not connect onr of the address lines, which mapped upper-case twice. A simple jumper addition to the motherboard was the only tweak needed to show the lower case. As noted elsewhere, lower-case descenders were not correctly located, although there were more ambitious mods that addressed that also. The original OS was developed by Randy Cook, and although NEWDOS was much better, Randy also produced a replacement DOS that was very sophisticated for its day, including device independence, file system and overlay features that were not present in competing systems such as CP/M.

Patrice Chouinard, from Montréal adds:
Curiosity, did you know that even with the TRS-80 Model I (yes model one) we had a 5 and 10 Mb hard disk drive (ok it was third parties mfgr). Somes of those hard disk were sold under the Apparat's Label. There was L-DOS (Logical Dos from Logical Microsystem). Also a DOS Called DR-DOS (yes) I think (but not sure but I can look back) it was in fact from Digital Research. There was a great magazine, very popular even before PC Mag and others. It was called 80 Micro and targetted to the TRS-80 world since early model I and that there was clones of the Model I.
Short and fun story (true one!)
At the time (1978) I owned a TRS-80 Model I. I also worked in an hospital. One of my co-worker wanted to see my computer. Radio-Shack had the "Carrying Case" for the computer. A set of two luggages. One for the computer and the other rather big one for the monitor.
I carryied out my TRS. In break-time, we set the machine on a cantina table, plugged it and turn it on. Whowwwww "Panik in the hospital". Every single piece of électronic monitoring équipment even two stairs down went completely crazy. Try to figure our faces when the chief medical found out why.
So that's fact... TRS-80 model I did generate a lot of radio freq.

8K versions by Stan Tishler:
When the TRS-80 Model 1 shipped some machines had an 8K chip due to a shortage of 4K chips. I had a model with a 7000+ serial number and when I upgraded to 16K I ended up with 20K. This was a real puzzle until Radio Shack quietly admitted that the early machines could have been 8K instead of 4K. In my case it was discovered by Godbout who worked with me installing the upgrade.

Ketlan Ossowski memories:
I was manager of a Tandy store (in the UK) when the TRS-80 first came out. Everyone thought it was a wonderful thing at the time and we sold a hell of a lot of them even though there was very little they could practically do at that time.
The prices were outrageous - £369.00 for the absolute basic model. Very expensive doorstop. :-)

About the TRS BASICs, Tim Hill adds:
The original unit came with "Level 1 BASIC" in a 4K ROM. This was very (er..) basic, created by Tandy.
Most units were upgraded with a new 12K ROM to "Level II BASIC", which was in fact a port of Microsoft (yes, them) MBASIC that was currently popular on CP/M machines, with some added TRS-80 twists.
Level II BASIC was in fact very clever, and though it was in ROM was carefully designed for expansion. When a disk drive was added (with TRSDOS 2.1 or similar) you got something called "Disk BASIC". However, this was in fact a bolt-on to Level II BASIC that integrated so smoothly that most users didn't even realize this. The rationale was to keep memory consumption low by combining the ROM BASIC with a set of RAM based disk extensions.

Once the 3rd party community got wind of this, a number of independent vendors used the same extensibility of Level II BASIC to create additional variants. As I recall (could be wrong, though), "Level 3 BASIC" was one such, and eventually Microsoft also created their own extended version.

Another interesting tidbit of information, from Brad Lineberger:
The original level II basic had a "key bounce" problem.  This would cause a key stroke to duplicate on occasion.  These versions of the ROM would display "Memory Size" instead of "Mem Size" (as later versions did).  They managed to squeeze a fix in to the existing 12k roms by reducing the overhead of some of the text strings (Such as "Mem Size", and the 2 digit error codes).

Richard Harding recalls:
In 1976 I worked at a new software development shop in Norristown, PA owned by an ex-IBM software engineer, John Brown. John dis-assembled the Radio Shack TRS-80 operating system and created his own disk operating system which was a screen-oriented Program Designer. In other words, to program a master file ( let's say a contact file ) instead of writing the program line by line, we would create the fields on the screen with the space bar hitting it the number of times we wanted the length of the field to be and then write the name of the field underneath it (eg: Field 1, "first name", 12 characters; Field 2, "last name", 20 characters etc.). After the entire record was developed on the screen, John's compiler reduced the whole program to machine language and set it up for screen entry. John's DOS used index keys, had sequential file handling and a very fast sort routine. I did application programming using the system to the amazement of our clients.

And, John didn't stop with that! Next he wrote an interface to drive a Winchester, 10MB hard disk using the TRS-80 floppy drive only to boot the system. The Winchester drive was in a cabinet about the size of the desk I'm writing this on and had only recently been made available to Main Frame and Mini-Computers. No one ever conceived of a micro-computer having a huge, hi-speed disk unit like a Winchester drive, except John Brown!

John finally took his DOS to Tandy, Radio Shack, demonstrated the system to them in the hopes of making it the Radio Shack Standard DOS with which developers could write application programs for the TRS-80 and businesses could buy Radio Shack computers. Sound like a brilliant idea?? It was but Radio Shack told John that they were in the computer selling business and didn't need any software in order to sell their computers! Those were the brilliant, forward thinkers of 1976.

I lost track of John Brown after those years but still have his Screen Development operating manual somewhere in my computer memories. And I still have my fond memory of him, a true computer genius of his time.

 





 
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