Followed the link Intel said : ----------------------- The following table lists the supported system bus frequency and memory speed combinations. To use this type of DIMM... The processor's system bus frequency must be... DDR400 800 MHz DDR333 800 or 533 MHz (Note) DDR266 800, 533, or 400 MHz -------------- Does this prevent me from using DDR400 on 533MHZ FSB for sure?