All I know is that it is an option which is not in my BIOS
P5E3 (standard) manages that thing by itself, @ 400FSB I can only run my 1600Mhz RAM @ 1333Mhz CL6 with a automatic PL of 8, I try to force PL of 7, but the system becomes unstable... I guess this is because I have 8GB of RAM
all in all PL is a good feature for those that have it as you can boost memory performance
John