I'm able to run 4x1GB Crucial Ballistix DDR3-1600 memories at 1600 7-7-7-18 1.80V on my P5K3 Deluxe. So ever P35 chipset can support 4x1GB memories at 1600 CL7. I don't see why X38/X48 chipset cannot run 4x1GB at 1600.