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From: jimomura@lsuc.UUCP (Jim Omura)
Newsgroups: net.micro.6809,net.micro.trs-80
Subject: Re: CoCo Memory Expansion
Message-ID: <943@lsuc.UUCP>
Date: Fri, 29-Nov-85 08:27:49 EST
Article-I.D.: lsuc.943
Posted: Fri Nov 29 08:27:49 1985
Date-Received: Fri, 29-Nov-85 10:02:09 EST
References: <405@ucdavis.UUCP>
Reply-To: jimomura@lsuc.UUCP (Jim Omura)
Distribution: net
Organization: Barrister & Solicitor, Toronto
Lines: 29
Xref: utcs net.micro.6809:623 net.micro.trs-80:508
Summary: the 64K barrier mmu's, pia's


     Mark, there's been a lot written on this topic.  See if you can get
back issues of the Rainbow or Hot CoCo.  In brief, you can expand pretty
far.  The new Tandy CoCo has a new PIA which may help.  The problem with
software stems from the fact that the CoCo banks in 32K pages.  If you
address only 64K (the limit of most 8 bit processors), and you have to
have the top addresses reserved for IO, then that limits your OS design
options.  You'd have to put your OS in the top page completely to have it
all there and bank the bottom half, but with a bit of the top page used
for parameter passing.

     The Colorburst is the only unit I know that expands the Color Computer
properly for position independant systems (like OS-9 and Unix).  It has a
6829 MMU which can bank 2K or 4K pages.  It can be bought with 64K RAM
for about $500.00 or with up to 1 Meg. of RAM.  I think it comes with RAM
disk software too. sp 


]
so it's immediately useable.

                                      Cheers! -- Jim O.

-- 
James Omura, Barrister & Solicitor, Toronto
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