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From: Fleysher.wbst@XEROX.COM (Dan Fleysher)
Newsgroups: net.micro.atari
Subject: Re: 16-bit upgrade for the 800XL, 130XE, etc.
Message-ID: <860128-070207-1228@Xerox>
Date: Tue, 28-Jan-86 10:02:07 EST
Article-I.D.: Xerox.860128-070207-1228
Posted: Tue Jan 28 10:02:07 1986
Date-Received: Thu, 30-Jan-86 05:19:28 EST
References: <8601272322.AA01905@mitre-bedford.ARPA>
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re: dropping a 65816 into your Atari 800XL in place of the 6502, to
upgrade it to 16 bits:  Note that ANTIC (the screen display chip) is
also an 8 bitter, so you would have to confine your display RAM to
within 64K addresses.  That's a real bummer - because one of the real
advantages of lots of memory would be to have several alternate screens
in memory at once and switch between them for animation, etc.  Also,
having usable RAM above the display area violates Atari 8-bit software
architecture, which always puts the display area at the top of available
RAM - the extra memory would not be usable by most 8 bitter programs
(but you could make RAM disk(s) out of it).

Then there's the problem that none of the existing memory decoding
handles more than 8 bits.  Also, you'd have to find a place to put the
additional memory chips without destroying the RF shield - a packaging
nightmare.

Sounds like an awful lot of work to me, and when you finished up you
would still not be able to run ST programs because of instruction set
differences between the 65816 and ANTIC and their ST equivalents.
Unless you want the experience of tearing apart your 8-bitter and
learning something, I think you'd be further ahead to buy a new ST.  (Of
course, those of us who use our 8 bitters for word processing, game
playing and bulletin-board-calling don't really need 16 bits anyway...)

	Dan

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