I have motherboard "ASUS P4S800" and P4 2.4C. When hyper-threading is on, kernel finds two CPU, but only one is used and swap become aggressive (after one day it is about 800 mb). When hyper-threading is off, swap is about 20 - 30 mb. PS. Last kernel which support hyper-threading is 2.4.22-2040. All latest version does not work.