Compiler Options

Jeremy Chadwick freebsd at
Fri Nov 10 22:24:48 UTC 2006

On Fri, Nov 10, 2006 at 11:34:22AM -0800, Jason C. Wells wrote:
> I have set CPUTYPE=p3 in make.conf.  When I compile my kernel I see 
> -march=pentium3 as I expect.  I also see -mno-mmx and -mno-sse are set 
> which I do not expect given that -march=pentium3 is used.  I presume 
> that I want MMX and SSE since my processor supports it.  What options do 
> I set and where do I set them to get a kernel properly tuned for pentium3?

The kernel will "support" MMX and SSE -- that is, any programs (root
or userland) which use MMX/SSE will work just fine.  That is: any
programs built with gcc can indeed support MMX and SSE operations.

The kernel itself _will not_ use any SSE or MMX operations when built.
This is because these optimisations are known to break the FreeBSD
kernel.  This applies to all i386 architectures, and probably 64-bit
architectures too (not sure).

CPUTYPE=p3 (or pentium4, or any other type) will not change this

| Jeremy Chadwick                                 jdc at |
| Parodius Networking               |
| UNIX Systems Administrator                   Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP: 4BD6C0CB |

More information about the freebsd-stable mailing list