Just finished running the promised half power test,
Here's the results:
QX9650, watercooled (Storm G5, Swiftech 665 pump and mcp320 rad)
Asus P5E (bios 602)
WinXp
Prime95 v25.5 running small fft test
Room temp/rad intake temp =27c
333 x 12 readings @ 1.336v vcore under load:
Coretemp 66-64-64-64
Realtemp 56-54-54-54
333 x 6 readings @ 1.336v vcore under load: (had to trim the vcore a little
as there was less full load droop at the lower clock speed)
Coretemp 52-48-50-50
Realtemp 42-38-40-40
So, starting with Realtemp I took a rough "average" of 54c for 333x12, and 40c for 6x333, with everything being equal apart from the core speed there should be an ideal of 50% power reduction, so,
x6 temp minus room temp should be half of x12 reading minus room temp:
54 - 27 = 27
40 - 27 = 13
pretty close to the theoretical 50%, now Coretemp, I used an "average" of 64 and 50, so:
64 - 27 = 37
50 - 27 = 23
way off the mark for the QX Cpu
Looks Like Realtemp is a keeper for this rig.
Iidle temps don't seem to be accurate though, with speedstep and other powersaving options turned off there was a temp difference of 1c at most between 6x and 12x core speed at idle.