Not necessarily.....Some versions of Pentium III's have SSE 1. The only problem with those processors is that they are too slow to run PCSX2 (well at least in the long run when speed will be increased thus requiring more cpu power). Also don't forget that AMD Sempron's are variants of the AMD K7 family. The Sempron's also have SSE1 but Im stuck on the question why they didnt add SSE2 in them. Considering the fact that new Celerons have it. I know Sempron's have SSE 1 because I own a Sempron 2500+ 