At right around 2200Mhz, the memory controller on my poor tetest-bed Core i7 920 just would not give me any more clock speed and would start dropping channels. By lowering the clock speed, I was able to tighten up the sub-timings to get the modules to run at Cas 8 at just over 2000MHz and Cas 7 at just over 1900MHz, if you choose to run this set at a lower speeds. But then again this is a kit meant to run at 2133MHz, so you will want to get what you pay for and use them at the rated speed.