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From: dyer@harvard.UUCP (Steve Dyer)
Newsgroups: net.micro.pc
Subject: PC/AT fast xtal warning
Message-ID: <604@harvard.UUCP>
Date: Mon, 13-Jan-86 12:41:30 EST
Article-I.D.: harvard.604
Posted: Mon Jan 13 12:41:30 1986
Date-Received: Wed, 15-Jan-86 07:58:18 EST
Organization: Aiken Comp Lab, Harvard
Lines: 19
Keywords: XENIX probs

I would like to point out a problem I discovered with using a faster
crystal in my PC/AT when I installed SCO XENIX V.  I had been running
quite successfully for months under DOS with an 18.4 mhz crystal, as
opposed to the standard IBM 12 mhz crystal.  During the XENIX installation
process, and occasionally and unpredictably while running XENIX subsequently,
processes would get SIGSEGV (seg violation or memory fault) sent to them.
There was no way to predict which processes would be affected or when.
Dropping back to 12 mhz stopped the problem.  I would like to solicit
opinions from knowledgable parties on the cause of this phenomenon and
its solution.  I suspect that the memory management hardware was stressed
lightly, if at all, under DOS, and the higher clock rate can produce
glitches in the 6 mhz 286's on-chip memory management hardware.  I am thinking
about installing a new 286 chip which is rated at 10 mhz (20 mhz xtal)
and trying the experiment again.  Any other suggestions?  Anyone else
see this problem?
-- 
/Steve Dyer
dyer@harvard.harvard.edu
harvard!dyer