MAME actually gets slower with each new release or so they say. The goal with the emu is to preserve the games I think so they dont focus on the speed part. Thats a shame because somebody ought to start optimizing the code. For example some late shoot em ups (1998-2000) can get a bit slow with lots of sprites moving round.. , and thats with a Pentium 4 2,4 ghz system.
I tried MAME on 030 also, it was extremely slow. I think loading Bombjack was like a couple of minutes or so... hmm. Ive heard its almost playable on 060 though.