TRS-80 Fragmentation

Fred Cisin cisin at
Fri Apr 27 10:11:25 CDT 2018

On Fri, 27 Apr 2018, Bill Gunshannon via cctalk wrote:
> CP/M ran on the Model I and the Model III.  CP/M was a very adaptable OS.

CP/M required RAM where the TRS80 Model 1 and 3 had ROM.

An unmodified TRS80 (model 1 or model 3) could not run unmodified CP/M.

FMG? marketed a relocated CP/M for the TRS80.  But, moving CP/M to a 
different area of memory wasn't a satisfactory solution.  It worked, and 
was CP/M, but few commercial CP/M programs would work with it, since 
they assumed that the TPA (Transient Program Area) would be where it 
usually was for CP/M.  But, it let me use TRS80 Model 1 to teach beginning 
basics of CP/M in my disk operating systems class.  (such as creating a 
zero length file to restart a program)

Parasitic Engineering (Howard Fullmer (later chief engineer at Morrow) 
had a company in Berkeley) marketed a sandwich board for the CPU, and 
another for the FDC, that altered the memory map, and also provided for 
8" drives.

Omikron in Berkeley made a similar setup.

I had both.  Neither were cheap.

Later, in the Model 3 days, there were some more relocations and adapters 
for CP/M, such as FEC, Holmes, Hurricane labs, Memory Merchant, Micro 
Craft. Was Montezuma Micro (Ron Jones?) for Model 3 or model 4?

> Tandy wasn't the only one who tried to do better.  Look at the NEC APC.
> Quad Density Double Sided 8" disks. High density color graphics with 256
> colors.  Dismal failure in the market because it wasn't fully "IBM
> Compatible".
> The follow-on NEC APC/III was a great big step backwards.

Or DEC Rainbow.  Or Sirius/Victor 9000.  Tandy wasn't the only one who 
thought that a "better" MS-DOS machine would be preferable to a clone.
There were many companies who made MS-DOS machines with various levels of 
compatibility, who had 80 track per side (96tpi) drives, such 
as Burroughs ET2120, Canon AS100, Rainbow, Eagle, IBM PC/JX, Monroe, 
Otrona (although their documentation writers misinterpreted 50h (80) as 
50! as discussed here 6 months ago), Siemens, Televideo TS1603, Toshiba 
T300, . . .

The Toshiba T300, for example, was reasonably compatible, other than 80 
track per side disk format, and they swapped the video memory location 
between CGA and MDA.  I ran PC-Write on one of them (I patched PC-Write 
for the other video memory).  Later, I loaned 2 of them to the California 
NMRI division of Toshiba for them to read disks.  Unfortunately, they 
returned them after they were finished.

Grumpy Ol' Fred     		cisin at

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