RE: [patch]K6-2/K-III compile option

Michael Cummins (mjcumm@isa.mim.com.au)
Fri, 1 Oct 1999 09:20:17 +1000

> -----Original Message-----
> From: Anders Fugmann [mailto:afu@bording.dk]
> Sent: Friday, 1 October 1999 2:40
> To: Michael Cummins
> Subject: Re: [patch]K6-2/K-III compile option
>
>
> Michael Cummins wrote:
> >
> > K6-2 and -3 support is a fantastic idea. AMD are king of
> the hill at the
> > moment and its good to see some support emerging in the
> linux kernel.
> > Quick questions though.
> > Does K6-2/-3 support need to be in the gcc/egcs
> compiler or what?
> Yes. It adds -march=k6 when compiling. This option is avaiable in the
> gcc 2.95 and egcs and pgcc.
> Is also anables som mmx routines, which currently only are used by the
> Athlon processor.
Maybe I'm mixed up but I thought the K6 didn't have anything like mmx,
But the 3DNow instructions set in the -2 and -3 version was AMD's
alternative to mmx.
And the Athlon was just adding an extra instruction set which is similar
to Intel SIMD implementation.

I think I can guess that what you actually mean is that gcc only has two
AMD style options.
-march=k6 means k6 without any mmx-stlye instructions
-march=k7 means Athlon with mmx and SIMD style instruction
ie not differentiation between the k6 vanilla and the k6-2 and -3.
Is that the problem?
Shame there's not a -march=mmx alternative which covers both
pentium MMX, K6-2, and K6-3. Though I suppose the instructions
sets are different so this would cause a problem.

What about -march=3dnow??? Would that be more plausible?

Michael Cummins

>
> > What part of the kernel build process is effected
> by this (ie where
> > does the optimization get started)?
> Compile time.
> > Do you need updated compiler or header files?
> No. Just the latest gcc. see http://gcc.gnu.org
>
> > Thanks
> > Michael Cummins
> Anders Fugmann
>
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