I recently bought a sapphire amd radeon 6870 and have been getting what seems like strange performance in games. For instance crysis plays on highest settings at 28-35 fps (1920 x 1080), but that only goes up to 40-60 fps on lowest settings with no AA, which to me seems weird. V sync is off. here is my setup:
Processor: Core 2 Quad Q8400 @ 2.66 ghz
Motherboard: Intel DP45SG Extreme Series
Power Supply: 600w (both 6 pin plugs are connected to the card)
Memory: 8gb 1333mhz DDR3
Graphics Card: Radeon 6870
More aboutframerates radeon 6870
See what happens if you overclock your CPU, lowering the settings makes the game more CPU bound.