It runs in asymmetric mode, L-shaped mode, flex mode, or whatever each manufacturer calls it. Right now, I have 2x2GB. Max RAM read speed is 16GB/s. If I add another 1GB stick I have around (I don't put it in because it's virtually useless for my purposes so far), Max read speed is still 16GB/s, something that single-channel DDR3-1333 CL9 cannot achieve. It drops to 8-9GB/s some time during the benchmark, which leads me to believe that 1GB is not in DC mode.