It's a SL4X2 and it should go higher, as I pushed it 3 years ago up to 2.14 GHz (http://valid.canardpc.com/show_oc.php?id=2114877) for validation, but now it's not very cold, so its limit is around 2 GHz. The other Pentium 4 1.4 Ghz Willamette s423 I have (B2 revision) is worse, while the Intel Pentium 4 1.5 Ghz Willamette s423 is between those two.