Will Woods (wwoods@xxxxxxxxxx) said: > Again: the only difference between i586 and i686 is the CMOV family of > instructions, which are generally *slower* than the i586 version. > > You can read Linus' detailed explanation here: > http://ondioline.org/mail/cmov-a-bad-idea-on-out-of-order-cpus > > Building for i686 gives *no* real performance benefit[1], but breaks > support for i586 machines - Via C7-based netbooks, AMD Geode (e.g. the > OLPC XO-1), and so on. > > -w > > [1] except on in-order CPUs like Atom and the original Pentium Actually, in some testing I did, the fasted was '-march=i686 -mtune=generic' (which was ~1% faster than '-march=i586 -mtune=generic'), tested across Core2Duo, Athlon64, and Atom. Twiddling the instruction scheduling (-mtune) invariably made things worse, across the board. Bill -- fedora-test-list mailing list fedora-test-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-test-list
