oc pci express frequency?

what exactly does this do? would it increase the speed of my graphics card?

the bios has a setting for this, it goes from 100-200...set at 100 right now (default)

 

On the nvidia 9xxx series uses the PCIe clock as a reference clock for the core. Read here. Normally overclocking the PCIe buss doesn't help any, though it can help if your running SLI and can only run each card at 8x. Also keep in mind that the PCIe bus is a multiple of 25. So: 100 x 25 = 2.5Ghz (PCIe 1.1 spec). Also overclocking the PCIe bus to far can cause data corruption on sata controllers that run off the PCIe bus. I normally run 120Mhz (3Ghz) just because. Though when not running in SLI it doesn't make much if any of a difference.