The mobo may only support the Willamette core processor... Not sure, but I have a socket 478 mobo and it says Prescott on it, so I'd assume it will only work with Prescott core processors? Don't have a diff type P4 to test out on it though. If you can find a cheap P4 that's faster than yours you might as well try it. I bought a 2.8GHz Prescott P4 for $30 off a guy once. Those are the best of the P4's, but they run HOT.