In most systems, 2*2GB is faster, as they are designed to have paired memory, and gain twice the bandwidth when they are paired. My system prefers memory in groups of 3, so I bought 3*2GB way back when I put it together. Consult your motherboards manual for the ideal setup, but I'm betting it works best in dual memory mode. Though, for gaming purposes, it often won't have major performance losses in single channel mode, but it isn't ideal.