I constantly run Myth 2 off of OS9 which is really annoying. When I do play it on OS X its incredibly choppy, like some sort of built in lag. I have a g3 processer, 500Mhz and I'd really love to play it on OS X.
also if they all are choppy, try disabling/enabling some stuff, like "hide underwater objects" and whatever else you see in the prefs menu that can speed your myth up
