TRS-80 Question

[Fred Cisin]

>>>> There's a 2K hole in the Model I memory map above the ROM
>>> Is this the hole that causes stock Model I to not run CP/M?

>> NO.
>> The problem with CP/M on TRS80 is that CP/M expects RAM from location 0 on
>> up.

On Tue, 19 Apr 2022, Charles Dickman wrote:
> When I was a freshman at Purdue, I lugged my Model III to my dorm room and
> connected to the ECN network with a 300 baud modem. I used a local editor
> and wrote a Pascal program to upload my Pascal source to the dual processor
> VAX-11/780 (Google George Goble), ea or eb, (I don't remember) that was
> used by our introductory programming class. The terminal program I had was
> something I found in Byte magazine in assembler and I modified it for the
> TRS-80. I had BASIC, Assembler and Fortran on the TRS-80 M III, so it was
> probably all in assembly.
>
> There was an article in Byte about CP/M for the TRS-80 Model III that
> described a hack to swap the ROM for RAM. The idea was to invert bits A15
> and A14. That would move the ROM and keyboard from 0000 to C000. There was
> a spare bit in some 4 bit register, so all you had to do was cut a couple
> traces and insert some XOR gates. I remember doing the modification on a
> Saturday while listening to the Purdue football game on the radio. I put it
> all back together and it worked. WoHo!
>
> At that point though I had no access to CP/M or where I might get it legal
> or otherwise, but I was good to go when I found it.
>
> I still have the computer and I still have the Byte copy. So 37 years later
> I should try to complete the project.
>
> -chuck

There were numerous hacks for TRS80 CP/M.
FMG sold a relocated CP/M for stock TRS80
Mnay programs weren't compatible, but it WAS CP/M, and adequate for 
teaching CP/M basics to my class, such as creating a zero length file for 
program restarting, etc.

Omikrom ("Mapper")
Parasitic Engineering ("Shuffleboard"?  Howard Fullmer's company)
Both of those were one daughterboard in the Model 1 to remap memory, and a 
daughterboard in the Expansion Interface to add 8" capability


There also some for model 3, including
Montezma Micro (Ron Jones?)
Hurrican Labs,
FEC?
Holmes?
Micro Craft?


When Radio Shack came out with the Model 4, which had built-in suitable 
memory map, they sold "CP/M Plus" (3.0?)
That would probably be the best to work with, and likely the easiest 
to find.

--
Grumpy Ol' Fred     		cisin at xenosoft.com