3dnow, mmx, k6-2 optimizing?

Conrad J. Sabatier conrads at cox.net
Mon Sep 13 12:10:33 PDT 2004

On Mon, 13 Sep 2004 12:23:18 -0500, Puna Tannehill <puna at imagescape.com>

> I've been looking for possible flags, optimizations, really anything 
> that would help me setup my laptop to use mmx and 3dnow.  I've updated
> /etc/make.conf to -march to the drum of a k6-2, but I'm not even sure 
> if mmx and 3dnow are being taken into consideration for compiling and 
> such, especially for Xorg.
> I did some googling and found people who used CFLAGS like -mmmx and 
> -m3dnow, but when I run with those options, they fail and said to be 
> invalid.  they don't appear in 'man gcc' which should have been the 
> first place i looked.  I'm not finding anything in terms of compiling 
> or configuring Xorg to use 3dnow or mmx, or even how to check to see 
> if they are automatically detected and used.
> Any thoughts?
> Puna

I don't know why those flags would not be working for you; I've been
using them for quite some time now on my Athlon (32-bit) box.  One
oddity I just noticed very recently is that, with the recent patches to
"make", the CPUTYPE variable seems to be ignored now, which is why I
explicitly added the "-march" flag to CFLAGS.  Also, note that I don't
use "-mmmx -m3dnow" for kernel builds; you don't want to be doing this,
as it can easily break things in the kernel, but for general builds
and port builds, it's fine:

CFLAGS= -O3 -pipe -march=athlon -mmmx -m3dnow

# buildkernel variables settings

COPTFLAGS= -O3 -pipe -march=athlon

Conrad J. Sabatier <conrads at cox.net> -- "In Unix veritas"

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