How to detect P4 Thermal Throttling?

[omv]

A friend and I have been searching, but unable to find a utility that shows when a P4 is in thermal throttle. Does such a beast exist at all?!?

 

[pm]

I work for Intel but I don't have any inside knowledge of this feature.

BUT, I have done some empirical tests. First, I uplugged the fan while running a benchmark (Prime95) and noted the benchmark result while monitoring the CPU temperature. I posted the results of that experiment here about a year ago. Unfortunately, the results of this test left too big an error on what temperature correlated with which benchmark result because the temperature rose faster than the benchmark could complete. So then I put a rheostat on the CPU fan and dialed the fan speed, let the CPU default to a fixed temp and then benchmarked it. What I found was that there was a fairly steep onset to throttling. Around 82C (number from memory, I did this about a year ago and I can't seem to find my notes), the CPU performance pretty much dropped off completely. Up until that point performance was fairly constant (within a percent or two).

 

[RalfHutter]

X-bit Labs did this test of P4 thermal throttling a few months ago, check out their methodology.

 

[MrThompson]

Check out page four of this blurb from Intel. Note the temp sensor your motherboard reads is in the cool part of the chip. The sensor the CPU uses for throttling is in the hottest part of the chip. Because of this, the CPU can be throttling momentarily and you won't see a difference in the temperature the motherboard reads. Sneaky stuff...

Here's another good read from Intel on throttling.