I broke an old 1.6 P4 a few weeks ago, so I went to fry's to pickup their 3.0GHz P4-E (prescott, boxed) they had on sale. I dropped it in, set voltages to by cpu, and ran it. It booted fine, but the BIOS kept yelling at me that the CPU type was invalid (on a Abit IS7).
Ran motherboard monitor 5: idle temp was 60C (!) where my 2.4C OCed to 3.0GHz idles at 41C. When I ran Sandra's benchmarks, it jumped to 75C in only ten seconds, and my temperature alarms went off, and the CPU thermal throttled! When I tried the stock cooler that intel put in the box, the CPU got so hot the thermal alarms turned on 5 seconds after booting and stayed on...71C idle!
I replaced my 2.4C, OCed it, and ran the usual benchmarks, and the OCed 2.4C ran cooler at full load than the 3.0GHz idles!
Maybe I got a bad one, and I knew Prescotts were hot...but 60! at idle!
So, I took it back to the stooge at Frys and he didn't seem the least bit surprised, especially since another customer had just returned another cpu for the same reason.
Looks like my next CPU/Mobo upgrade will be FX5x.