If it says 266 or 333, then it must be DDR, since if it was SDRAM it would read either 100 or 133! And Diehardware is correct, the KT3 Ultra supports only DDR with 184 pins. If it wasn't DDR, it wouldn't even POST. Hopefully, you are running PC-2700 ram @166 fsb. I recently upgraded my CPU to a Thoroughbred and am running at 166 and it makes quite a difference.