Yes,as long as the motherboard supports it,but all modules must be the same type.you can add higher speed modules, they just won't run at their full speed.
So long as they have the same CAS latency, timings, and recommended voltage,your motherboard would probably just automatically underclock the faster one.Having said that I wouldn't really recommend mixing ram, as there's no guarantee it wont cause problems & ram is pretty cheap.
So long as they have the same CAS latency, timings, and recommended voltage,your motherboard would probably just automatically underclock the faster one.Having said that I wouldn't really recommend mixing ram, as there's no guarantee it wont cause problems & ram is pretty cheap.
I've used different brands of memory with no problems,but as I said,there's no guarantee.