TRS80s and TRSDOS (Was: Microsoft open sources GWBASIC

Fred Cisin cisin at
Thu May 28 17:15:38 CDT 2020

> > > Outside of CP/M were *any* mainstream American home computers Z80
> > > based before the C128?

>> Yes.  TRS80.
>> It had a memory map that was incompatible with CP/M.  BASIC in ROM at the
>> bottom, and RAM at the top.
On Thu, 28 May 2020, Liam Proven via cctalk wrote:
> Which one?

"TRS80" was the original one.   LATER, when other derivative models came 
out, it began to be called "TRS80 Model 1".
(Note: either Roman Numerals or arabic)

Similar to the way that "The Great War" began to be called "World War 1". 
If you wade through old archives, you will find that the phrase "Word War 
2" or "WW2" came into existence as a phrase or name BEFORE the existence 
of "World War 1" as a phrase or name.  (Bar bet: "Which came first, 
'World War 1' or 'World War 2'?")

Similarly, depending on the clientele of the bar you frequent, and 
dependent on relatively non-existent archives for settling the bet, 
"Single Density" never existed as a phrase until AFTER marketing started 
to call MFM, "Double Density".  ("Which came first,...?")

TRS80 base model had 4K of RAM (upgradable to 16K), and "Level 1 BASIC" in 
ROM at the bottom (preventing easy use of CP/M), which was a derivative of 
Li-Chen Wang's "Tiny BASIC", changed to single precision floating point 
instead of 16 bit integer, etc.
David Lien's "User Manual For Level 1" was highly regarded as a beginninng 

Upgradeable to "Level 2" (Microsoft BASIC) for about $100.  (with some 
string handling, trig, error messages, etc.)

The TRS80 [Model 1] default sale package at $600USD was the computer, an 
ordinary cassette recorder (CTR-41?), cable to connect cassette recorder 
(#26-1201?), and video monitor, which was the same as a certain model of 
cheap RCA TV, without tuner (might have had some isolation?) and painted 
gray.  That model of TV (in white) shows up in the background on kitchen 
counter in "Married With Children" (a USA sitcom whose lead character, Al 
Bundy, is similar to Victor Meldrew of "One Foot In The Grave")
There was a little known POSSIBILITY to order one without the monitor and 
cassette for $400 (I did.)

The TRS80 [Model 1] had three 5 pin DIN connectors on the back for Video 
(Composite), Cassette (26-1201 cable) and power supply (a large cord 
And a 40 pin expansion port.  There were a few peripherals for the 
expansion port, such as a "cable" (with some circuitry) for driving 
Centronics syle printers.  YES, their first printer was built by 
Centronics, so they were a major contributor to the misuse of calling the 
36 pin Blue Ribbon connector "Centronics".

They came out with an "Expansion Interface", with sockets for an 
additional 32K of RAM, a "Centronics Port" (34 pin edge connector and 
26-1401 printer cable), a continuation of the 40 pin expansion port, an 
FDC (WD 1771, configured for 5.25" FM/SD with inadequate data separation), 
and an empty compartment with connector for an "RS232 Adapter" (the RS232 
adapter did not make good electrical connection, requiring modification 
or twiddling).  The Expansion Interface had its own power supply, 
identical to the computer power supply, but had a large open space inside 
to hold both power supplies.  Cords going out the back, but a hole or 
notch could be made to get rid of the excess length/route of the 
computer power suppies cord to the computer.

The connection (40 pin to 40 pin) between the computer and the Expansion 
Interface was fraught with problems, and resulted in NUMEROUS recalls, 
no-charge modifications, including one model with a box in the middle with 
buffers, some with an added wire to bypass the buffers, etc.
Since the edge connectors were without gold plating, there was constant 
connector problems, easily significantly reduced by bolting the computer, 
E.I., and a power strip to a piece of plywood.

The initial operating system was written by Randy Cook.  It was OVERLY 
sophisticated, and he never finished it.  It had multi-level passwords, 
and used a hash table to speed up directory searches.  The first version 
released was "Version 2", before Randy Cook OK'd release, with a few 
mimeographed pages (influencing Apple to call the first release of theirs 
"Version 2.2").  Radio Shack quickly released version 2.1, with ALMOST 
everything ALMOST working.  Randy Cook and RS parted company partway 
through writing V2.2.  There were bugs in 2.1.  Apparat patched a lot of 
them, and came out with "APR-DOS" that included a list of hundreds of bugs 
that they had fixed, and a statement that it was only for use by 
legitimate owners of TRSDOS.  It is not clear whether that was an amazing 
disassembly, or whether they had access to some or all of the source code. 
RS lawyers considered the "only supplemental" terms INADEQUATE, since 
somebody could buy and use that without spending $15 at RS for TRSDOS. 
There are many undocumented rumors such as that Apparat tried to claim 
that it was changed enough to be non-infringing but that Randy Cook's 
lawyer (I can't remember his name, but he sold a small terminal program) 
ran the boot file as if it were a program, using one of the master 
passwords (hashed, so multiple sequences of letters worked) and pressed 
two keys (R,V) resulting in a full screen copyright message saying RANDY 
COOK popping up.  That shot down the "non-infringing" argument.  RS 
immediately patched the "easter egg" to read "TANDY CORP" instead.
As part of the settlement, Apparat rewrote their OS to be non-infringing 
and thus came out with a MUCH better OS - "NewDOS-80"
V2.2 was patched enough to be usable, and V2.3 was reasonably stable and 
became the standard OS.

Randy Cook really wanted to finish implementing some spectacular features. 
Some folks funded development and he started work on TRSDOS 3.0. (with 
"Automated Computer Software Service?)
He didn't finish.
Scott Adams (Adventure International, NOT THE CARTOONIST) took over 
and got him working on VTOS 4.0
He didn't finish.
Logical Systems, Incorporated (AKA Lobo Drives) came out with an expansion 
interface for the TRS80 [Model 1], with 8 inch drives, and double density, 
using a WD 179x chip.  The WD 179x can not write one of the Data Address 
Marks that model 1 TRSDOS uses (rumored to have been a result of 
transposed columns in a datasheet).  So, they needed a patched operating 
system.  They bought license for VTOS 4.0 and hired a significant portion 
of the best known TRS80 assembly language programmers (Roy Soltoff, etc.). 
They succeeded in completing LDOS 5.0.  It was magnificent, and competed 
head to head with NEWDOS-80.

Later, Radio Shack bought rights, and marketed LDOS5 as TRSDOS 6.0.
Because model 1 TRSDOS had been a work-for-hire, AND was never finished 
(nor were 3.0, 4.0), in spite of being the designer of a major family of 
operating systems, Randy Cook had never made any significant money from 
it!  BUT, when Radio Shack started marketing TRSDOS 6.0, Randy Cook was 
getting royalties from THAT.

The "TRS80 Model 2" was a completely unrelated machine.  It was sold as a 
business computer, with Z80, 64K RAM, and 8" drives.  Radio Shack sold an 
operating system for it that they called "Model 2 TRSDOS" (V1.3?).  NO 
connection or similarity to TRS80 [Model 1] TRSDOS.
But, the Model 2 could also run CP/M.  Lifeboat and "Pickles And Trout" 
sold CP/M for it.  And RS eventually sold "CP/M Plus" (CP/M 3.0) for it.

Later, a revised version of the Model 2, called the "Model 12" came out.
And a 68000 co-processor board for the "Model 16", Model 16B, and "Tandy 

The "TRS80 model 3" was essentially a model 1 repackaged into a single 
desktop case.  Radio Shack sold "Model 3 TRSDOS 1.3" for it (not to be 
confused with "Model 2 TRSDOS".  But NEWDOS-80 and LDOS worked great on 
it, so VERY few people ran the "Model 3 TRSDOS".  and then, when RS sold 
TRSDOS 6.0 (LDOS 5.0), that becsame a popular OS for it.

Inability to run CP/M without modifications, and <80 column screen 
continued to haunt it.
RS came out with the "TRS80 Model 4", in the same case as the Model 3, but 
not painted gray, with 80 column screen, and more versatile memory 
In addition to TRSDOS 6.0, "CP/M Plus for Model 3" (CP/M 3.0) was 
They also sold a luggable version called the "TRS80 Model 4P"

I am unaware of any existence of mdels 5,6,7,8,9,10,11,13,14, nor 15.

So, the transition was
TRS80 [Model 1]
TRS80 Model 3
TRS80 Model 4 and 4P

Independently, there were
TRS80 Model 2
TRS80 Model 12
TRS80 Model 16, 16b, Tandy 6000

Separately, along the way, there was the
Radio Shack Color Computer (6809), and later the Tandy Color Computer.

TRS80 Model 100 (8085 tablet/notebook Kyocera machine similar to NEC 8201, 
PC8300, and Olivetti M-10)
(believed to be the last machine that Bill Gates did significant coding)
Model 102
Model 200

Radio Shack Pocket Computer
(rebadged Sharp and Casio machines)
Note that the FIRST one was called "TRS 80 Pocket Computer", and LATER 
became known as the "PC-1".

After-PC (august 1981), Radio Shack made some MS-DOS machines such as the 
model 2000, and eventually PC-DOS machines.

> I know nothing at all about these but I believe the III ran Xenix
> on a 68000 and had some resemblance to the Apple Lisa,
Model 16 could run Xenix.

> But it claims the Model III is compatible with the Model I. (Wut?)

Yes.  essentially a repackaged model 1.

Your remarks on it are confusing the III with something else.

> It very quickly all becomes rather surreal and I rapidly lose track
> (and interest, TBH.)

Then the above will bore the hell out of you.
You can keep a copy buried for reference, or go through the sequence all 
over again later.

"Accessory" items that warrant discussion include the Percom Data 
Separator and Doubler, the RS Votrax, etc.

I hope that others will make corrections and fill in gaps so that 
eventually this could be accurate enough to be meaningful.
Particularly Allison! and Eric Smith, who worked at Apparat long after the 
above incidents were a topic of discussion.

Grumpy Ol' Fred     		cisin at

>> For those parts of the world that didn't have TRS80:
>> Note: Radio Shack TRS80 model 1, 3, 4 were a straightforward transition.
>> 4P was a luggable version of the 4.
>> Model 2 (and 12, later) was a TOTALLY unrelated product consisting of a
>> "business" computer with 8" drives, with CP/M available.
>> Model 16 had coprocessor board with 68000.
> Er. Right.
> So it goes:
> Model I → Model III → Model 4
> *And*
> ↘
>  Model 2 → Model 12 → Model 16
> ... ?
> Where do the VideoGenie and Coco fit in?

Coco was a COMPLETELY independent model.  There are unsubstantiated 
rumors about Motorola pushing RS to do it.

Videogenie was not Radio Shack.  They were based on the TRS80 [Model 1]. 
PMC-80 (a rebadged Videogenie) was marketed briefly in USA
I've heard that Dick Smith (Australia) marketed one as the "System 80"
It would qualify as a NON-CP/M home computer other than being based on 
TRS80 [Model 1]

More information about the cctech mailing list