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Date:      Sun, 16 Jun 2002 18:00:04 +0100
From:      David Malone <dwmalone@maths.tcd.ie>
To:        Stephen Montgomery-Smith <stephen@math.missouri.edu>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: CPU_ATHLON_SSE_HACK
Message-ID:  <20020616170004.GA28556@walton.maths.tcd.ie>
In-Reply-To: <3D0CA144.27B68749@math.missouri.edu>
References:  <3D0CA144.27B68749@math.missouri.edu>

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On Sun, Jun 16, 2002 at 09:31:32AM -0500, Stephen Montgomery-Smith wrote:
> I saw in the release notes for 4.6-stable that there is an option in
> LINT for CPU_ATHLON_SSE_HACK.  I looked all around LINT and the Freebsd
> web site, but I couldn't find many details.  What are SSE instructions,
> and how would I know if my BIOS had enabled them?

If you don't know what SSE instructions are, then you probably don't
need to worry about them. They are a a sort of extended MMX
instruction. They aren't used by the kernel, but you need kernel
support to use applications which use SSE (there aren't many of
these).

To figure out if they are enabeled on your processor you can look
for the features line in dmesg and see if it contails SSE, for
example:

walton 24% fgrep Features /var/run/dmesg.boot
  Features=0x387fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,PN,MMX,FXSR,SSE>

Note that older Athlon processors don't do SSE at all and motherboards
which forget to enable them on newer processors are rare.

	David.

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