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 ci...@xenosoft.com
