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Path: utzoo!dciem!nrcaer!cognos!geovision!alastair
From: alastair@geovision.UUCP (Alastair Mayer)
Newsgroups: comp.sys.atari.st
Subject: Re: Memory reliability
Message-ID: <134@geovision.UUCP>
Date: Mon, 10-Aug-87 12:17:10 EDT
Article-I.D.: geovisio.134
Posted: Mon Aug 10 12:17:10 1987
Date-Received: Fri, 14-Aug-87 03:23:08 EDT
References: <8708010521.AA25524@ucbvax.Berkeley.EDU> <4401@sunybcs.UUCP>
Reply-To: alastair@geovision.UUCP (Alastair Mayer)
Distribution: world
Organization: Geovision Corporation, Ottawa, Canada
Lines: 22

In article <4401@sunybcs.UUCP> leo@gort.UUCP (Leo Wilson) writes:
>If my own memory serves me correctly, IBM PC's don't actually use the parity
>bit, it's just there. Seems I remember some people simply leaving the chips
>out, or moving their flaky/bad chips to the parity bit socket because it
>didn't matter at all. Did any of the software use the 'extra' bit? I may

I'm afraid your memory doesn't serve you correctly.  The parity bit
most definitely *does* matter in IBM PC's and at least some of the clones,
if not all.  There is hardware in the memory circuitry to check the
parity and generate an interrupt in the case of an error.  (Been a while
since I soldered a PClone together, I don't remember the chip #s).
Some of the clones have a DIP switch or jumper setting that lets you
disable this if you don't want to install the extra chips.
  One of the irritating things about the IBM boot up sequence was that,
while it did do a memory check, it didn't tell you *where* the problem
was if it found one, it just stopped.  Some of the clones have friendlier
startup checks.
-- 
 Alastair JW Mayer     BIX: al
                      UUCP: ...!utzoo!dciem!nrcaer!cognos!geovision!alastair

"He sure looks like plant food to me." -- Audrey II