People are asking this question a lot in various threads so hopefully making a new post will help people see it easier. The purpose in CPU Margin Enhancement is to help provide better FSB clocking with cheaper C2Ds.. that is, according to intel. In practicality this option only seems to play absolute havock with peoples systems. If you are experiencing odd system instability, not able to get FSB clocks as high as you could, or having strangely low DRAM frequency barriers I strongly advise you try one of these P5Q Series mBIOSes. The pack contains modded BIOS files for all P5Q series boards using code before asus added CPU Margin Enhancement.