Memory dividers do reduce the speed of the RAM. You use dividers if you have cheap RAM that has low OCing potential. If you use a 9:10 divider on DDR400 RAM with 200HTT/FSB, then your RAM would be at 180MHz. But raising the HTT/FSB will counteract the reduction of RAM speedz. If you raised your HTT/FSB to 222MHz, then you will have 200MHz RAM speed.