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Date: Sun, 7 May 2006 21:30:54 +0200 (CEST)
From: "Vincent Blondel" <vincent@xtra-net.org>
To: freebsd-current@freebsd.org
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Subject: I_686  MMX / 3DNOW / SSE / SSE2 ?
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Hello everybody,

I am preparing a new FreeBSD server ( 2x Athlon Mp ) that will host 30 jails serving apache/tomcat websites.

I was just writing my kernel config file when I remarked that option CPU_ENABLE_SSE is disappeared and is now automatically
added when I_686 is configured ( and naturally CPU_DISABLE_SSE is not enabled ).

So in this context, I use 'CFLAGS= -O2 -pipe -fno-strict-aliasing' and 'CPUTYPE?=athlon-xp' for compiling kernel but when I
look at file /usr/src/sys/conf/kern.mk I see all kind of mmx/3dnow/sse/sse2 are disabled and if we analyzed a bit one line
comping from a kernel compilation we get such a line ...

cc -c -O2 -pipe -fno-strict-aliasing -march=athlon-xp .. -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow -mno-sse
-mno-sse2 ..

So, finally, there is something I don't understand, what is the goal of 'CPU_ENABLE_SSE' if we disbable all kind of
optimization a bit further and is there any sense to set CPUTYPE to athlon-xp in such a way ?

Many thanks for your remarks, comments, explanations.

Vincent.