Re: Pentium M config option for 2.6

[Jakob Oestergaard <jakob@unthought.net>]

On Sun, Jan 04, 2004 at 01:33:58PM +0100, Tomas Szepe wrote:
> On Jan-04 2004, Sun, 13:27 +0100
> Mikael Pettersson <mikpe@csd.uu.se> wrote:
> 
> > IOW, don't lie to the compiler and pretend P-M == P4
> > with that -march=pentium4.
> 
> What do you recommend to use as march then?  There is
> no pentiumm subarch support in gcc yet;  I was convinced
> p4 was the closest match.

Use the same as for P-III.

The P-M has the same instruction decoder (and execution unit) setup as
the P-III, which is *very* different from P-IV (which has one decoder
only, and then a trace cache for the decoded uops).  This is an
important difference from a code generator point of view.

>From reading Intel's optimization guides, it seems to me like the P-M is
pretty much just a slightly enhanced P-III (more cache AFAIR) which
happens to get shipped with a good mobile chipset - and that package
together is called Centrino.

That would also explain why Centrino leaves the P-IV based laptops in
the dust ;)

Cheers,

 / jakob