One key difference between the GeForce 6800 AGP and GeForce 6800 PCI-E is memory clock frequency: while AGP 6800 cards ship at 350MHz (700MHz effective), the memory used on PCI Express GeForce 6800 cards runs 50MHz slower, at just 300MHz (600MHz effective). This means that PCI Express GeForce 6800 cards are effectively giving up 3.2GB/sec of peak memory bandwidth to their AGP cousins, which can have ramifications at higher resolutions (or when AA/AF is used). Of course, PCI Express GeForce 6800 cards have the added ability to be linked together (via SLI) for added performance.

While the stock clock speeds of the 6800's graphics core and its memory pales in comparison to today’s latest high-end and even mainstream cards, the balanced 12-pipe approach NVIDIA has implemented is more than enough to outpace the GeForce 6600 GT, we also got a nice performance boost from overclocking. The GeForce 6800’s arch nemesis, the RADEON X800 XL, is more than a handful for the GeForce 6800 PCI-E, delivering performance that actually rivals the more expensive GeForce 6800 GT. For now the GeForce 6800 PCI-E is somewhat safe, as X800 XL cards are still very difficult to find at retail, and nowhere near their manufacturer suggested selling price, but this will really begin to change next month, as a wave of X800 XL cards from third party manufacturers are coming very soon.