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From: davidg@cory.Berkeley.EDU (David Gaertner)
Newsgroups: comp.sys.ibm.pc
Subject: Compaq286 crashes at full 8Mhz; doesn't crash at 8/6Mhz speed.  WHY???
Message-ID: <3133@zen.berkeley.edu>
Date: Thu, 30-Jul-87 03:40:53 EDT
Article-I.D.: zen.3133
Posted: Thu Jul 30 03:40:53 1987
Date-Received: Sat, 1-Aug-87 04:49:07 EDT
Sender: news@zen.berkeley.edu
Reply-To: davidg@cory.Berkeley.EDU (David Gaertner)
Distribution: na
Organization: University of California, Berkeley
Lines: 29
Keywords: DMA JRAM

[I'm not superstitious, but I do believe in line eaters....]

I have two Compaqs 286 which are the versions that have 3 speeds: 6 Mhz
(common), 8 Mhz CPU with 6 Mhz I/O (fast), and 8 Mhz for both CPU and
I/O (high speed).  When I set the first Compaq to high speed, it worked
just fine.  The second one, though, just crashed after a couple of
minutes, showing nothing but a cursor on the monitor (and the monitor
looked as if it lost its vertical hold).  Rebooting had the same
results over and over again.  Both systems are identically configured
so I tried switching my JRAM memory boards, and the bad machine still
acted badly.  I even went so far as to back up the bad machine's hard
disk and restore it on another machine, but the software worked fine on
the other machine.

I read something about early Compaqs having a DMA problem, so maybe
that is my problem.  So my question is, is that the problem?  Is the
8 Mhz I/O speed too much for the (buggy?) DMA chip I have?  If not, or 
if so, what can I do?

I would really appreciate some info from people who have dealt with
this problem before.  And, no, the simple solution won't work: I have
to use the high speed mode, not the common or fast modes.  Thanks in
advance....


David Gaertner
davidg@cory.Berkeley.edu via ucbvax 

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