If your RAM clock speed differs from the 1600 MHz that this Corsair RAM is clocked at, your motherboard's BIOS should reduce the clock speed of whichever RAM sticks are higher clocked to match the lower clocked speed. For example, if you have one stick of RAM that is clocked at 1333 MHz, your motherboard should reduce the speed of this RAM to 1333 MHz. You can also mix CAS latency, but you may have to manually tweak various settings in the BIOS to get it to run stable. Honestly, for the price of RAM, and for as much as you seem to be wanting to add, I'd just replace your current RAM entirely with something new so you do not have to worry about stability issues cause by weird compatibility issues with different RAM sticks.