what is there to explain? I said that the XP is cooler, clock for clock the T-bird. If you had your t-bird overclocked, then the xp is even cooler....
The PAL8045 is a good heatsink...
however, if you're comparing temps after shutdown on the heatsink, there is a reason the T-bird is warmer: THe less efficient PCB "holds" heat much moreso than the new organic fiberglass PCB of the XP. Therefore, the chip holds less overall heat during operation, and during shutdown, the heatsink doesn't have to do any work on an XP chip.
It should not be colder under load compared to the t-bird though. Unless you are running the XP chip at a lower voltage. A T-bird and XP, both at 1400mhz, both supply roughly the same amount of heat into the heatsink as per this review:
Overclockers.com Glaciator II review. Pay close attention to the heatsink-thermocouple (heatsink mounted measurement above the CPU core and inside the heatsink base) results for both XP and T-bird chip: They are
both 17.4C above ambient, indicating that despite the t-bird being ~9W warmer at max wattage,
both chips push roughly the same amount of heat into the heatsink, clock for clock. If you were over volting the t-bird more than the XP chip, then there's your reason why the heatsink is hotter. Voltage does more to increase chip wattage than raw mhz. For example, a .1V increase on a T-bird chip results in an increase of roughly 6.5 watts.
Mike