Originally Posted by n0ahg
XP reports HT as a real core so it can't take advantage of it and can cause more stalls and therefore increase the overhead. This would support you link!
The weird part is that I can't tell what OS those tests were ran on - I must be missing the test machine specs. I can find hardware, just not the OS. It was done in November 2008, and Vista was out in January 2007.. so likely it was Vista? Not sure.