On Tue, 2003-06-10 at 00:17, John Haxby wrote: > Christos E. Chrisostomidis wrote: > > > Most of the RPM packages shipped with RH9 (and older), come for a i386 > > target. > I think that you'll find that the RPMs are optimised for the i686 but > will run on an i386. They are actually compiled with -march=i386 -mcpu=i686 which means "generate actual i386 instructions, but put them in such an order to bring the most benefit to i686 systems". The difference between that and -march=i686 (which means "generate i686 instructions" and implies -mcpu=i686) is usually small. > Applications like sendmail and samba, being > somewhat I/O bound, are unlikely to benefit from the marginal > performance that you'll get with marginal extra performance that you get > by sacrificing i386 compatability. Also, strange bugs may be triggered by compiling apps with optimizations not widely tested. > Things like the gimp and MP3 > encoders/decoders, that is, CPU bound applications, get rather more > benefit from sacrificing i386 compatability and these are largely taken > care of anyway. Yes. Usually, only heavy-duty multimedia apps are likely to benefit from tough optimizations, and even then the gain may not be big. Still, if there is an absolute need for that, one may try something like this: # cat /root/.rpmrc optflags: athlon -O2 -march=athlon-xp -mfpmath=sse optflags: i686 -O2 -march=pentium3 -mfpmath=sse # (replace pentium3 with pentium4 if appropriate) This way, the i686.rpm packages will actually be optimized for Pentium3 (or 4) processors, and athlon.rpm packages will be optimized for AthlonXP processors. There will not be any backward compatibility, you will have to run them on those CPUs. For CPUs with large caches (probably 512k or above, but i'm not sure) it may make sense to try -O3 instead of -O2. Well, try it anyway, it may just yield better results anyhow. But it largely depends on the application, there is no hard rule. I'm not sure of the benefit of it for typical Internet applications. Also, you need a new gcc (i think 3.2 or newer, but i'm not sure). -- Florin Andrei "Privacy is such a 20th century concept." - Darren Reed
