Im using 2 sticks of Crucial 256mb CL2.5 DDR on my P4S333..I was running it at 16x144fsb with DDR at 1:1 ratio with 2.5v and fast settings..then I changed it the other night to 16x141fsb with DDR at 4:5 ratio, default settings but at 2.7v..still rock solid and I gained about 600 points on the SiSoft memory tests