[vetinari]

Your argument would be more valid when comparing for example the PPC32 to PPC64, but for IA32 vs AMD64 you are missing:

- IA32 is register starved ISA, AMD64 is not. It has doubled the amount of general registers.

- AMD64 doesn't have to support the x87 FPU baggage. As a result, it is simpler to deal with fp math.

[pyre]

IIRC AMD64 does support x87, but Window/Linux have chosen to 'standardize' on SSE. In this respect x86-64 is a 'version' of x86 where all processors are guaranteed to have SSE and not need x87.