The q6700 will work on a variety of chipsets like g31, g41, p31, p35, p43, p45, p965, p975x, x38, x48 etc. The qx6700 extreme will only work on a limited number of chipsets p965, p975x, x38, x48, p35. Most HP were lower end lga775, usually g31, p31, which are just enough to run a c2q, therefore cheaper. Most of the higher grade chipsets for HP were aftermarket vendors like Asus, msi especially, but did not include OC ability. Only clean bios, high grade boards could support both extreme cpus and OC.