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Date: Mon, 15 Sep 1997 10:54:58 -0700 (PDT)
From: William Maddox <maddox@p-1.Eng.Sun.COM>
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To: Michael Beckmann <beckmann@nacamar.net>
cc: hardware@FreeBSD.ORG
Subject: Re: Parity trouble with Asus mainboard
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On Mon, 15 Sep 1997, Michael Beckmann wrote:

> Greetings,
> 
> I had installed 8 x 32 MB parity SIMMs in an Asus P65UP5 Rev. 2.04
> mainboard with Pentium Pro card P6ND in it. The system is equipped with one
> PPro 200 CPU. Unfortunately, when I install 4, 6 or 8 of these SIMMs,
> FreeBSD gives me a parity error and panics directly after the copyright
> notice during boot. With 2 x 32 MB, it seems to run OK.
> 
> This, however, happens only when I enable ECC in the BIOS. When I disable
> ECC/parity, the system runs fine with 256 MB installed. I made world on the
> latest 2.2-stable in this configuration, no problem.
> 
> I also tried the same SIMMs in a Gigabyte 586 HX board, and there I can
> boot and run just fine with ECC enabled in the BIOS (it's an NT system,
> though).
> 
> Any ideas ? It doesn't look to me like the SIMMs were faulty. Maybe a
> problem with the parity chips ? I also exchanged the mainboard with another
> one of the same type, but found the same problem.
> 
> Michael

Are you sure these are true parity SIMMs?  Some cheap SIMMs use "logic
parity", which just fakes a parity bit for older MBs that require it.
These will not work with ECC, and should be avoided in any case.
Also, you describe these SIMMs as 2 x 32, 8 x 32 and so forth.  In
standard nomenclature, the "32" is the width of the SIMM, i.e., 32 bits.
Parity SIMMs are 2 x 36, etc.

Admittedly, this doesn't explain why the Gigabyte board worked, unless 
somehow the ECC was disabled behind your back.

--Bill