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cc: alex@fa.tdktca.com (Alex Nash), bmk@fta.com,
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Subject: Re: FreeBSD works with Cy486DLC processors? 
In-reply-to: Your message of Tue, 18 Jun 1996 13:45:57 +0200.
             <199606181145.NAA18166@ra.dkuug.dk> 
Date: Wed, 19 Jun 1996 05:16:26 -0400
From: "Jacob M. Parnas" <jparnas@jparnas.cybercom.net>
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In message <199606181145.NAA18166@ra.dkuug.dk>you write:
>In reply to Alex Nash who wrote:
>> 
>> Brant M. Katkansky wrote:
>> > 
>> > > I installed FreeBSD 2.1.0-RELEASE a couple of weeks ago and since then I
>> > > have been having programs exiting with signals 10 and 11, making my system
>> > > too unstable to work as a dedicated e-mail server and as a PPP to Ethernet
>> > > gateway.
>> > 
>> > [snip]
>> > 
>> > I had one given to me not too long ago.  Mine is plagued with various
>> > sig 10 and 11's, same as yours.
>> > 
>> > Here's the interesting part - disabling the internal and external cache
>> > makes the problem worse.
>> 
>> This should be fairly easy to explain: You have bad SIMMs.  While your 
>> program is running, erroneous results are returned from RAM and the 
>> processor tries to execute them.  Your program subsequently seg faults 
>> due to an invalid instruction.  If your cache works properly and your 
>> SIMMs don't, the cache can mitigate these effects since RAM accesses are 
>> less frequent (thus missing the odd inverted bit somewhere :) ).  Disable 
>> the caches and now you will be much more likely to see a bad SIMM in action.
>> 
>
>Hmm, just to add another datapoint:
>I can run 2.1 on my 486DLC board, but -current will panic within
>2 minutes with a page fault or semilar. I have a very strong
>feeling that our Cyrix/486DLC support leaves much to be desired,
>as I can make the system run better (not error free) if I disable
>the Cyrix code in locore.s. It seems that using the BIOS defaults
>(both caches on) runs alot better than what we are trying to do
>to it.....
>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>Soren Schmidt             (sos@FreeBSD.org)             FreeBSD Core Team
>               So much code to hack -- so little time.
>

You might try reinserting the SIMMS.  I remember that we bought tons of
expansion SIMMs for hundreds of computers, and not once did an original
or memory upgrade SIMM become defective even after years of use.

Jacob