Samsung RDRAM on a Samsung PCB offers the best overclocking potential for RDRAM....virtually all Samsung RDRAM modules produced in the last six months can hit somewhere between PC1100 and PC1140, and some (maybe 25%) can hit PC1200. When you exceed PC1100 speeds, you need to have decent case cooling/circulation, as RDRAM tends to produce a good amount of heat at those speeds.
If Corsair simply puts their name on Samsung RDRAM and PCBs, as I have heard, then you should have no trouble hitting PC1100, assuming the memory was produced in the last six months. If you can't hit at least that memory speed, then your motherboard or processor is at fault. Only a small minority of Abit TH7-II mainboards can hit memory at 533MHz (PC1066) due to their 400MHz clock generators; all P4T-E mainboards with the ICS 600MHz clock generators can clock to 533MHz and beyond if you use the mainboard DIP switches (as necessary to access the AGP/2 and PCI/4 dividers).