performance boost when going to 64 bit in most situations. Core 2 chips suffer a small penalty when going 64 bit. I suspect this is due to the
Core2 has some micro-optimizations which are only enabled for 32b mode, which is an interesting choice. AMD tends to be biased towards HPC or at least serverish stuff, which is 64b-oriented...
cache hit rate suffering which, with a traditional north bridge, would have proportionally more effect.
I can't think of negative effects of x86_64 other than possible higher memory overhead for apps that use lots of pointers. compilers are a typical example, but perhaps some sparse matrix stuff, too? code density in x86_64 mode is not much different in mcmodel=small (for instance, it's not the case that every offset in branch and memory reference instructions become giant...)
it'll be most interesting to see how AMD has optimized Barcelona... _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
