On the X86 there are 3 types of instructions:

Integer instructions(most code)

Floating Point instructions(complex math,needed an FPU on 386)

Vector instructions(comparable to altivec called MMX,SSE2/3/4)

The Hackintosh OS X emulates vector instructions on A PIII using

an earlier version of the vector extension.

Most OS X system code runs in integer instructions,

so expect slowdowns at running .apps like garage band or gimp.