You mean 3:4,if you have the P4B533 mobo then 1:1 will be 3:4 in the bios and 4:3 will be 1:1 .Are you trying to boot up at 155fsb at 3:4?.You might not be able to handle it at that high without trying to raise your voltage,don't go past 1.7 volts max.At 150FSB at 3:4 is 400DDR,you can do it😀