Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!um-math!hyc
From: hyc@math.lsa.umich.edu (Howard Chu)
Newsgroups: comp.sys.atari.st
Subject: Re: Request info: 1040 RAM upgrades
Message-ID: <528@stag.math.lsa.umich.edu>
Date: 29 Dec 88 06:33:09 GMT
References: <480013@hpdml93.HP.COM> <527@stag.math.lsa.umich.edu> <1304@accelerator.eng.ohio-state.edu>
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Reply-To: hyc@math.lsa.umich.edu (Howard Chu)
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In article <1304@accelerator.eng.ohio-state.edu> DAVISM@kcgl1.eng.ohio-state.edu (Michael T. Davis) writes:
>	I am a bit confused over the "2.5 megabyte" specification.  To
>paraphrase Howard Chu, he writes that he installed a memory expansion
>board with 2 megs on-board into a 1040.  How does this yield 2.5 megs?

The board comes with 32 sockets. There are originally 32 256K RAMs in the 1040.
(The chips in the 1040 are soldered directly...) The Atari Memory Control Unit
can only handle 32 chips. Ok... 2 meg, in 1Mbit chips, is 16 chips. Why leave
the control unit idle on the other 16 addressable chips? Configure the board
to use the 16 1Mbit chips, as well as 16 of the old 256Kbit chips. That all
adds up to 2.5 MB. After this upgrade, you're left with 512KB worth of 256Kbit
RAM lying around, with the other 512K of the 1040's original 1 MB still in use.
--
  /
 /_ , ,_.                      Howard Chu
/ /(_/(__                University of Michigan
    /           Computing Center          College of LS&A
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