Traditionally when you overclock your FSB, the PCI and AGP slots would also be affected since they used fixed diviers (1/4 and 1/2 for instance on a 133 FSB). When you up the FSB, you'd also up the PCI and AGP ports. Obviously not good since alot of cards would crap out on a 37-38mhz PCI bus.
Enter PCI/AGP lock. Basically the ability to change the FSB without affecting the PCI and AGP clocks. No longer a fixed divider (it's more of a floating divider) the board will keep the PCI/AGP (very close too) the desired 33/66mhz clocks regardless of how much you overclock the FSB.
Unfortunatley it's not availible on AMD64 boards yet.
I checked the manual on my 8RDA and I don't see it as a feature. Is it not implemented on this board or is it just done automatically and not stated in the manual?