As Orcvader said, quad channel RAM will only run in dual-channel if using a SB/IB processor, since the memory controller on these CPUs only supports dual channel. When it says quad-channel on the RAM, this simply means that it is certified to run in a quad-channel configuration, provided that your CPU memory controller supports this (SB-e processors have quad-channel memory controllers). In the real world though, quad channel memory has little performance difference compared to dual channel anyway.