Quote from Patussay :

the video card, drivers, settings are not the problem, is the dual core, this problem need to be fixed with a patch or something

Actually it is the Video drivers and the dual core when combined , The ATI drivers 5.12 and newer have dual core optimizations built into the drivers so the driver uses both cores, Theres a fix expected (for ATI owners) in the next driver release (6.2)

This is not a game code problem .

SD.