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Date:      Fri, 31 Aug 2001 04:01:14 -0400 (EDT)
From:      "Albert D. Cahalan" <acahalan@cs.uml.edu>
To:        freebsd-stable@FreeBSD.ORG
Cc:        juha@saarinen.org, pahowes@fair-ware.com
Subject:   RE: FreeBSD and Athlon Processors
Message-ID:  <200108310801.f7V81EQ453022@saturn.cs.uml.edu>

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Juha Saarinen writes:

> It's probably not the Athlon CPU that's the issue for either FreeBSD
> or Linux, but the motherboard chip sets. From personal experience,
> the first Linux 2.4 kernels weren't very happy with VIA chip sets,
> which are commonly used for Athlon boards. It's mainly IDE issues
> (e.g. UDMA-66/100 support).

There are at least two major problems with VIA chips:

Any fast PCI device (often IDE) can cause data corruption.
VIA initially blamed this on a specific sound card that would
push the bus pretty hard, then offered a Windows hack that
would disable some performance features. After some trouble
finding a contact at VIA, Linux got the same hack. If you
don't have this hack... well maybe you just got lucky or did
not notice that your data is getting trashed. (with FreeBSD's
small user base, a data corruption problem like this one
might go unnoticed for a while)

If the CPU pushes the memory bus too hard, stuff goes wrong.
This was first noticed with some Athlon-specific assembly code
in the Linux kernel. The problem has also been seen by Windows
users running Photoshop. Sometimes the problem goes away if you
upgrade to a very large power supply. AMD has been having some
trouble running their new core on VIA motherboards; maybe the
new core hits the same problem on unoptimized code.

So problems will be less common with an OS that doesn't push
the hardware very hard, but do you really want to trust this
junky product? Maybe next year you will upgrade to a new gcc
that generates code that is fast enough to trigger a problem,
or you will install a gigabit network card that is aggressive
with the PCI bus. Don't upgrade that CPU next year either.




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