I have writted few days for conflict between my ram modules.Now i have one in second pc,its 5-5-5-15 667 mHz.In my pc is 5-5-5-18 800 mHz.So its not problem to set in bios lower frequency but will this two work together ?
It is 50% and 50%. If you mix them and if the PC boot then the ram will run in 667MHZ, until you OC the RAM to 800MHz. Just try it since you have both of them in hand, right?