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Date:      Sun, 2 Feb 1997 23:07:34 +0000 (GMT)
From:      Alan Cox <alan@cymru.net>
To:        terry@lambert.org (Terry Lambert)
Cc:        davem@jenolan.rutgers.edu, terry@lambert.org, michaelh@cet.co.jp, netdev@roxanne.nuclecu.unam.mx, roque@di.fc.ul.pt, freebsd-smp@freebsd.org, smpdev@roxanne.nuclecu.unam.mx
Subject:   Re: SMP
Message-ID:  <199702022307.XAA01582@snowcrash.cymru.net>
In-Reply-To: <199702022135.OAA08696@phaeton.artisoft.com> from "Terry Lambert" at Feb 2, 97 02:35:27 pm

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> Well, Sun generally does things right.  I was more concerned with
> a number of Intel motherboards where we are seeing APIC_IO problems.
> They seem to fail this case.

The intel boards get the hardware coherency right. After all its exactly
the same for dual CPU as for CPU and PCI master. Certainly some single
CPU boards get this wrong for specific cases. Just look at the matrox
meteor list ..

> I don't know what lists you follow, but just in the past two days,
> the has been a person on the FreeBSD SMP list running a motherboard
> with "improved cache handling" that seems to be barfing on something
> like this when APIC_IO is used... 8-(.

The APICs have a pile of little 'features'. Read the intel errata before
playing. Also if you have B stepping Pentiums (except the MMX) you might
as well stop on boot.

Early on there were several Linux cases of 'weird crash' that came down
to faulty boards/cache. Even some of them boards that worked fine single
CPU.

Alan





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