Microsoft open sources GWBASIC

Tony Duell ard.p850ug1 at
Thu May 28 12:53:47 CDT 2020

On Thu, May 28, 2020 at 6:38 PM Liam Proven via cctalk
<cctalk at> wrote:

> > Americans were oblivious to anything that wasn't in USA.
> Yes. :-(
> > Yes.  TRS80.
> >
> > It had a memory map that was incompatible with CP/M.  BASIC in ROM at the
> > bottom, and RAM at the top.
> Which one?

The Model 1 and Model 3. The Model 4 was like a model 3 at switch-on,
but you could write to an output port to shuffle things around, take
the ROM out of the memory map and have 64K of RAM. There was an
official  CP/M for the Model 4 (but I prefer LSDOS on mine...)

> As they're purely a theoretical concept to me and AFAIK I've never
> actually touched one, the profusion of models is very confusing, and
> I'm  not aware of an idiot's single-para overview.
> I vaguely know of:
>  • TRS-80 Model 100 (8085), pre-laptop portable
>  • Tandy 1000 (PC compatible)
>  • TRS-80 Model 2000 (*before* the 1000?! Also kinda-sorta PC
> compatible, nearly?)
>  • TRS-80 Colour, AKA CoCo -- 6809
>  • TRS-80 Pocket (no idea)

There were many TRS-80 'Pocket Computers'. All were essentially
re-badged versions of either Sharp or Casio machines. Sometimes with
minor differences, the Pocket Computer 2 is essentially a Sharp PC1500
but the keyboard layout is different so overlays for one do not fit
the other.

> Then there seem to be about 42 different computers called TRS-80 Model
> X where X is either a Roman or Arabic number under 1000, after which
> it all changed. Except 2000 comes before 1000. Obviously.
> The TRS-80 Model I, Model II, Model III, Model 4, Model 12, Model 16,
> etc. 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, which would

No, that's the Model 16 (think of 16 as '16 bit')

> seem to preclude any relation to the Model I & Model II -- and
> Wikipedia suggests that the Model II is totally different from the
> Model I.

It is. The Model 2 (which begat the Model 12 and the Model 16) could
run CPM from the beginning (IIRC there was no BASIC in ROM, just a
disk bootstrap) and had 8" floppy drives.

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

Sort-of. The Model 4 is compatible with the Model 3 (but the Model 4
does rather more). The Model 3 is related to the Model 1 (ROM at the
start of the memory map, maximum of 48K RAM, etc) but there are enough
differences to make them not-quite-compatible.A model 3 will not boot
from a model 1 disk, for example. The Model 3 has a double density
disk controller (which can also do single density), the model 1 is
single-density only. Perhaps the largest change is that almost all I/O
on the Model 1 is memory mapped, the Model 3 has them as Z80 I/O
ports. (But as so many programs read the printer startus _memory
address_ input port on the Model 1 to check that a printer existed,
etc, the Model 3 has the printer status port available both as memory
mapped or I/O mapped).

> It very quickly all becomes rather surreal and I rapidly lose track
> (and interest, TBH.)
> I suspect a graphic might be needed to disentangle it.
> > 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?

The Video Genie is not a Tandy machine. It was a clone of the Model 1
(almost) and ran the same software. Much as there were copies of the
Apple ][ doing the rounds in the Far East.

The CoCo is a totally different family, based on the 6809 (the other
machines used a Z80).

CoCo 1 (officially maximum of 32K RAM, but you could fit 64K chips and
access it all with some trickery)
CoCo 2 (offically up to 64K RAM, redesigned PCB and case but otherwise
compatible with the CoCo 1. The CoCo 1 has a 'chicklet keyboard', the
CoCo2 has something approaching a full-size one).
CoCo 3 (No longer based on the Motorola 6883 application note. The
6883 + 6847 chips are replaced by a custom Tandy IC called 'GIME'
(Graphics Interrupts Memory Enhancement). Some of the 'semigraphics
modes' no longer exist, meaning some software will not run. On the
other hand you could have up to 512K RAM, 80 column text, true lower
case, 640*200 graphics, etc)


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