Running steam on a Athlon XP 2400+ results in this:
Program received signal SIGILL, Illegal instruction.
0x08240471 in std::tr1::__detail::_Prime_rehash_policy::_M_next_bkt(unsigned int) const ()
The assumption would be that the binary was built with SSE2 instructions (because this is a rather common issue these days), which aren't supported in older CPUs. Note that the requirements do state that Pentium 4 or Athlon XP1500+ is supported. (And I'd rather it stay this way to keep in sync with the Windows version that does run under the same CPU.)
I suggest using "-march=i686 -mtune=generic" for gcc to make sure that the binary supports every processor that a typical linux distribution supports.
Note that the issue has already been reported
, but it doesn't use the requested issue format and isn't in the proper sub-forum.