Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!APG-EMH1.APG.ARMY.MIL!rbloom
From: rbloom@APG-EMH1.APG.ARMY.MIL (Robert Bloom  AMCICP-IM 3775)
Newsgroups: comp.os.cpm
Subject: Re: Looking for MP/M specs/documentation
Message-ID: <8902211431.AA09284@ucbvax.Berkeley.EDU>
Date: 21 Feb 89 14:20:04 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
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MP/M is a multi-user version of CP/M v2.2.  Each user gets their 
own 48k bank of ram, the upper 16k is the 'executive'.  The 
single processor is switched between users by bank selecting.  I 
don't know if CP/M itself must also squeeze in the 48k, giving 
each user their own copy of the os.  There is a Osborne-Hill 
guide to CP/M and MP/M with all the system calls - maybe still in 
print, it (the book, not the os!) was very popular at the time.  
MP/M gave the user too little memory, a slower than normal 
processor (due to sharing it with other users), and very 
rudimentary file control (user numbers).  Looked just like 
standard CP/M to the user, but with the user # in the prompt.
 
I'm much more familiar with NorthStar's varient of MP/M called 
TSS/C - each user got 56k of Ram to hold a copy of CP/M and their 
programs, the upper 8k did nothing but switch the z80 between 
banks and manage the disk(s) and printer(s).  There was also a 
32k bank dedicated to the system.  Worked well but slow.  (Five 
[!] users on one 4mHz Z80 - what did I expect!)
 
NorthStar (and I) replaced TSS/C with TurboDOS, a multi-
*processor* system - giving each user a dedicated (z80 or 8086) 
processor w/Ram with one 'master' processor w/Ram for shared 
resources.  Block diagram looks just like a LAN with all 
processors in one box.
 
Both systems generally ran only on S100 boxes.  Most s100 SBC's 
(Single-board computers) have TurboDOS drivers available.
 
Bob (rbloom@apg-1.arpa) Bloom