On Thu, Aug 15, 2013 at 09:12:52PM +0200, Dimitry Andric wrote: > On Aug 15, 2013, at 20:36, Konstantin Belousov <kostik...@gmail.com> wrote: > > Does the linux box defaults to pentium or higher for -march ? > > 64 bit atomics cannot be implemented in usermode on i386 on > > processors which do not have cmpxchg8b instruction. > > Ah yes, you are totally right, with -v it gives: > > COLLECT_GCC_OPTIONS='-O2' '-S' '-v' '-mtune=generic' '-march=i586' > > So we should really disable atomics for i486 and lower? Though I have > understood that there also some pentiums without cmpxchg8b...
I do not think that there was any Pentium-branded CPU which did not implemented cmpxchg8b. Some late 486 did provided cpuid, but I am almost certain that they did not have cmpxchg8b (cannot check anyway).
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