From: Johnny Hughes <mailing-lists at hughesjr.com> > All of that is probably true ... but the optimizations are already set > by default by the config.guess and autoconf and automake for almost all > RedHat SRPMS ... and CentOS doesn't change those, unless absolutely > necessary. Which is what I agree is most preferrable. > Therefore, for almost all packages on CentOS-3 they are --march=i386 > --mtune=i686 ... Maybe I need to look a bit deeper then. I could have swore I've seen many packages with Makefiles (after any autoconf) that clearly send to stdout a "gcc ... --march=i486". Maybe I'm thinking too much of just the kernel itself. > and for most CentOS-4 packages they are --march=i386 -- > mtune=pentium4 ... being that the default target is i386. Yep, I guess the --mtune=pentium4 was introduced with FC2+. I would recommend Intel backtrack though, because it's not the most ideal for other i686 architectures (only true P4 or Athlon). Although the performance hit is not that much. -- Bryan J. Smith mailto:b.j.smith at ieee.org