Messages in this thread | | | Date | Tue, 6 Jan 2004 07:07:22 +0100 | From | Jakob Oestergaard <> | Subject | Re: Pentium M config option for 2.6 |
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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
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