So, I got a Battlefield 3 recently, and my iMac wasn't doing good. I had to set on medium for decent FPS (30~40), and all low to play good on multiplayer. Then I read about overclocking ATI 4850 to desktop clock will increase the performance. So I tried to overclock using MSI Afterburner. I enabled unofficial overclocking, then I set the clocks on 625/990. The thing is, GPU-Z and CCC recognizes the clock as 625/990, but MSI Afterburner's graph is still on default, 500/880. So I ran the Furmark test, and the FPS and the score had no difference between defalut and overclock setting I tried. That means it actually did not applied to the graphic card. I need help on this. Is there something I'm missing? If you can, can you give me proper steps to overclock iMac?