Re: [gentoo-amd64] CFLAGS for Core2?

[Brandon Edens]

I generally check safe cflags.
http://gentoo-wiki.com/Safe_Cflags

I have a friend that has riced out Gentoo boxes twice now and had problems due
to the cflags he chose. Of course, your results may vary.

Brandon


On Thu, Sep 21, 2006 at 10:52:42PM -0500, Eric Augustus wrote:

> On Wed, Sep 20, 2006 at 04:25:12PM -0400, Jack Lloyd wrote:
> >
> > Tomorrow my new Core 2 workstation should be arriving, and reading
> > through the 2006.1 amd64 install notes and so forth, the recomended
> > CFLAGS for EM64T CPUs is -march=nocona. However as that is tuned for
> > 64-bit enabled Netburst rather than Conroe, I'm wondering if anyone
> > had thoughts on good flags. In particular as (to the extent that I
> > know anything about microarchitecture), Conroe seems closer to a K8
> > than a P4, especially with regards to pipeline length and execution
> > resources, I'm not sure that P4/Netburst tuning is the right thing to
> > do. But the GCC docs say that -march=k8 enables 3dnow, which Intel
> > chips don't have. So, right now the "seems likely" options would
> > be:
> >
> > -march=k8 -mno-3dnow -msse3
> > -march=nocona
> > -march=pentium-m -m64 [saw this suggested in the forums, seems like a bad idea]
> >
>
> I've got a Dell XPS 700 with an E6600, and, like you, wondered what were
> the "best" CFLAGS to choose. Lacking any solid directions, I went with:
>
> CFLAGS="-march=nocona -O2 -pipe"
> CHOST="x86_64-pc-linux-gnu"
> CXXFLAGS="${CFLAGS}"
> MAKEOPTS="-j3"
>
> Simple, and nothing fancy.
>
> I'm happy to say that my 2006.1 amd64 install seems to be working great.
> I'm running unstable, btw, which I've been doing on my old athlon64 for
> a couple years now.
>
> I'm still tweaking my kernel options though.
>
> P.S. It's amazing how fast a kernel builds and emerges happen on the new
> Core 2.
>
> --
> Eric Augustus
> shrike@×××××××××.com
> -----------------
> Are we on STRIKE yet?
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>