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Date:      Tue, 18 Jun 1996 08:32:28 -0700
From:      "Michael L. VanLoon -- HeadCandy.com" <michaelv@HeadCandy.com>
To:        Alex Nash <alex@fa.tdktca.com>
Cc:        bmk@fta.com, "Eloy A. Paris" <Eloy.Paris@ven.ra.rockwell.com>, questions@freebsd.org, hardware@freebsd.org, hal@wwa.com
Subject:   Re: FreeBSD works with Cy486DLC processors? 
Message-ID:  <199606181532.IAA16018@MindBender.HeadCandy.com>
In-Reply-To: Your message of Tue, 18 Jun 96 06:29:43 -0500. <31C69327.32639FD9@fa.tdktca.com> 

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>> > 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.

>> 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.

This is a good candidate for the cause on the second guy's
motherboard, since the problem gets worse when he turns off cache.

>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.

This is typically the cause with motherboards that have 486DLC chips
in them -- they're so cheap (usually just a 386 motherboard) that the
cache coherency circuitry is bad to nonexistant.

-----------------------------------------------------------------------------
  Michael L. VanLoon                                 michaelv@HeadCandy.com
        --<  Free your mind and your machine -- NetBSD free un*x  >--
    NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
        Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
    NetBSD ports in progress: PICA, others...

   Roll your own Internet access -- Seattle People's Internet cooperative.
                  If you're in the Seattle area, ask me how.
-----------------------------------------------------------------------------



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