Im using Amithlon on a core2duo, so speed isnt a concern. I dont really expect to be playing daytona usa, etc., but the emulated 68k cpu is far beyond any os4.x hardware running native ppc code, so cps2, neogeo, etc. are fine (even with my old athlon64 amithlon machine I could play the above at full speed, so with a machine twice or more the speed I can deal with the fact that mame gets progressively slower).