For starters, I am running Win 7-64bit with an Athlon 64 X2 4000+ on a Biostar GeForce 6100 AM2 board.
I have four 2GB sticks of DDR-2 PC 6400 RAM, and want to install all 8GB. Two of them are Corsair CL 4 and the other two are Super Talent CL 6. Can I mix the two different CAS latencies? If so, would it be best to put the CL4 in the first DIMM slots?
My machine has been running on the CL6 RAM for about 4 years.
Welcome, Newcomer. First, yes, you can mix them, but it is a bad idea. Mixing RAM often results in less than desirable outcomes. For example, your CL4 and CL6 can be mixed, but the CL4 sticks will be forced to operate at CL6. The manufacturer will label the RAM at its highest potential, thus if labeled CL6, that is the lowest timings that is stable.
Aside from the latency stand point, you also have to consider voltage. Similar to latency, let's say the CL4 sticks were designed to run at 1.5V, max, but the CL6 sticks require 1.7V. Mixing these kits will have unfavorable results.
Some of the problems you may encouter include, but not limited to:
2. Random crashing
3. Installed RAM does not equal usable RAM