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From: jhs@MITRE-BEDFORD.ARPA
Newsgroups: net.micro.atari8
Subject: Re: 6502 vs Atari
Message-ID: <8608222127.AA03543@mitre-bedford.ARPA>
Date: Fri, 22-Aug-86 17:38:03 EDT
Article-I.D.: mitre-be.8608222127.AA03543
Posted: Fri Aug 22 17:38:03 1986
Date-Received: Fri, 22-Aug-86 23:43:58 EDT
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Organization: The MITRE Corp., Bedford, MA
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According to someone at Atari who shall remain nameless, mostly because I
can't find the message with his name on it,  the 6502 in the XL/XE series is
indeed a custom version with internal tri-state buffers and a HALT line.
In some of the old 800 series, presumably the ones in which a new ANTIC chip
was added or something, there were external tri-state buffers controlled by
the HALT line, and a standard 6502.  One could drop in a 65802 in that circuit
and it should work.  Also, the same logic could be used in a XL/XE machine
to make a 65802 work.  One would just have to make a piggyback board to plug
into the 6502 socket (did someone say SOCKET?) and in turn provide the socket
for the 68502 and the tri-state drivers and the control logic.  The only thing
I am a little unclear on (not quite the same as nuclear) is how to halt the
65802.  Perhaps the ANTIC knows what it can get away with and all you have to
do is (carefully) halt the clock to the 65802 during the HALT signal period.

I suspect everything will fall nicely into place, given a piggyback board.


-John Sangster
jhs@mitre-bedford.arpa