I have a 2.66ghz MacPro with the x1900xt card and just realized how underclocked the card is when running OS X. I launched the game Return To Castle Wolfenstein and was expecting much higher FPS but was only able to get 125fps and even that wasnt constant. When I booted up Win XP Pro and launched the same game with the exact same config settings i was able to maintain about 360 FPS and had spikes of over 700 FPS which is way higher than what I can even get close to when running under OS X. I guess my question is....does anyone know how to fix this so I can get the full potential out of the video card that I shelled out and additional $250 for? Right now it performs only moderately better than my Powerbook G4 with only 64mb of vid ram. I have checked ATI Accelerator II and it doesnt support the x1900 or the x1600 yet. My Powerbook's ATI card is moderately overclocked and the difference is wonderful and has been stable for over a year.