SGI assembly reference manual. Pages 2-7
describe register usage for three ABIs (-32, -n32 -64, where these
latter two are running on 64bit hardware, and get to use 32 fp regs).
IA-32 Intel Arch & ISA Manuals. Also includes Intel's description
of EM64T instructions (oh my gosh, some of this looks almost exactly
like the AMD64 docs! Whatever could be going on?).
cpuid: site with simple SSE instructions
lists, as well as some arch info.