3dnow, mmx, k6-2 optimizing?

Puna Tannehill puna at imagescape.com
Mon Sep 13 11:33:29 PDT 2004

Erik Trulsson wrote:
> On Mon, Sep 13, 2004 at 12:23:18PM -0500, Puna Tannehill wrote:
>>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?
> You do not say which version of FreeBSD or GCC you are using.
> Gcc 2.95 (which is what FreeBSD 4.x ships with) do not know about MMX
> or 3Dnow, and will not take advantage of them.
> Gcc 3.4 (which is what FreeBSD 5.x comes with) does know about MMX and
> 3DNow and will take advantage of them when invoked correctly.
> The switches you mention (-mmx and -m3dnow) are valid for gcc 3.4 but
> not for gcc 2.95.

Apologies!  I'm running v5.3-BETA3 with GCC v3.4.2.

> You can look at the GCC documentation found at
> http://gcc.gnu.org/onlinedocs/ to find out what options are supported
> by which versions of GCC.

mmm, documentation...  Thank you!  I have added the options to CFLAGS 
in /etc/make.conf and am currently rebuilding world without any stops 
yet.  Although, there is probably little or nothing outside of X 
windows that those options might help optimize.  But I'll be 
rebuilding Xorg and XFCE right after I'm done with the world.

For those who are following, here are the pages that I found most 
useful as reference materials:

Intel 386 and AMD x86-64 Options:

X86 Built-in Functions:


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