> You can also press F10 during the countdown to unthrottle MAME. Assuming your machine > is reasonably fast, the countdown will run a little faster. Just remember to turn it > back on before you try to play.
Another option: holding down the Page Down key will unthrottle MAME to the maximum speed it can run at; let the key back up, and it returns to whatever setting it was at before you pressed it. I'm assuming this isn't specific to SDL builds on OS X.