Date   : Thu, 14 Jan 1993 17:59:11 GMT
From   : agate!spool.mu.edu!uwm.edu!caen!uvaarpa!concert!sas!mozart.unx.sas.com!sasrer@ucbvax.Berkeley.EDU (Rodney Radford)
Subject: Re: CP/M FOR TRS-80 MODEL III, 48K

R3DRS@VM1.CC.UAKRON.EDU writes:

>I have recently aquired a TRS-80 Model III, but with no software (other than a
>couple bootable TRSDOS V1.2 with nothing else useful on them).  Knowing that
>CP/M was a very popular replacement for TRDOS, i am interested in finding some
>sort of version of this operating system so i might make some use of this
>machine.  Could someone point me to a source for something i could use?
>I did find something that looked promising that came with a Z80 emulator for
>MS DOS, but i think that it might be for a 64K system (mine is 48K).  Is there
>a good CP/M source available through the internet?  Also, how about software?
> 
>                    Thanks in advance,  Dave Snyder   r3drs@vm1.cc.uakron.edu
> 

A stock (non-modified) TRS-80 Model III will not run CP/M as RS used the
lower 14K for EPROMs, memory mapped I/O space, and video memory. I have
heard of modifications to the Model III that will remap these into the 
upper 16K (basically remap the top two address lines), and then some other
hardware to handle the initial hardware boot (ie: a shadow EPROM at 0 that
can be mapped out, or something). Anyway, CP/M can run on it, but you must
get your soldering iron out (Or be lucky enough to locate one of the
retrofit kits for the Model III that just plugged in - I think it was a
daughter board that plugged into the Z80 socket, with the Z80 relocated to
the daughter board).

The TRS-80 Model IV, and the portable (actually more of a 'luggable') IVP
could run TRSDOS or CP/M. Maybe you could locate one of these....

Good luck.

PS: Rereading the above, I realized that I assume that you know that CP/M
    requires a contiguous RAM area starting at address $0000. Just thought
    I would point it out for the CP/M newbies...   ;-}

--
---
Rodney Radford          || Computer Graphics/Imaging
sasrer@unx.sas.com      || SAS Institute, Inc.
(919) 677-8000 x7703    || Cary, NC  27513