I just got 2 2gb sticks of Balistix Crucial. Can I still fill my last two dimm slots with my old RAM? 2 1gb sticks of OCZ. They are both 800mhz pc6400. The crucial RAM has CL-4-4-4-12. The ocz RAM is 4-5-5. My mobo guide says to use the RAM with the same CAS Latenc. Which number is the CAS Latency? My bios says its the first number, the 4. So far no problems with this setup but ive only had it for an hour or two.