A PII 300 was what I started building my cab with before someone donated
a P4. I was able to get semi-decent, playable results with Mame v 0.53.
Also played some older Visual Pinball tables, SNES, Genz, VisualBoy (not Advance
just the GB/GBC games), and the Atari stuff already mentioned. It even
hooked well to my dancepad for Stepmania, believe it or not.