Perhaps a better title would be something like "Why are P4 chips so much easier to cool than Athlon's?"
My dual Pentium II system is starting to show its age and I have been thinking about upgrading. Last January I upgraded my wife's computer to an Athlon XP 1700+. The performance is good, but the Volcano 7 HSF and stock Enlight PS sure make a lot of noise. You don't realize how much until you turn the system off and it gets eerily quite (unless my computer is also on).
After a little searching on quieter computers I came across this site (great site, BTW!). After reading about the issues with power dissipation, core sizes, heat spreaders, heatsinks, fans, etc., I'm still wondering why P4's seem to be so easily quieted compared to Athlons. For example, checking the wonderful tables at http://users.erols.com/chare/elec.htm
, I notice that an Athlon XP 2000+ has a power comsumption rated at 62.5W typical and 70W maximum. The "equivalent" 2.0A (1.5V) P4 is rated at 52.4W "thermal design power" (maybe roughly comparable to "typical"?) and no maximum given. However, judging from the P4 entries a little higher up, the thermal design power seems to be about 75% of the maximum dissipation (at least for the older cores), which in this case would make the max around 70W, the same as the Athlon. Yet the P4 is considered easier to cool (I'm working only with worst-case max power numbers here for simplicity).
The obvious first reason is that the P4 Northwood core die size is larger than either current Athlon core (i.e., Palomino and T-bred), which we know from, for example, Anandtech (http://www.anandtech.com/showdoc.html?i=1635&p=2
). Hence the P4 NW will have a larger area over which to dissipate the heat produced, i.e., a lower power per unit surface area (what's the proper term for this quantity? Areal power density?). One would think that the heat spreader would make this even better, but I read in another thread here (http://forums.silentpcreview.com/forums ... php?t=2037
) that the spreader is really to help physical issues (no crushed or scratched cores) and even out temperature hot spots, but in fact increases overall thermal resistance.
With the reasons given, the heat spreader seems like a reasonable trade-off. But why then wouldn't an Athlon benefit from a heat spreader? If the P4 core can be cooled so easily even with the heat spreader getting in the way, shouldn't an Athlon with similar power dissipation also benefit by a similar amount cooling-wise by having a heat spreader? Is there a flaw in my reasoning?
I am just musing about this because it seems a shame that the Athlons, even (or especially?) the T-breds, appear to be so problematic for quiet computing considering they have such a great price/performance ratio. You can buy an Athlon and expensive HSF combo (like the SLK800 plus Panaflo) for less than the stock equivalent P4. I figure I'll probably end up going with a P4 for my next computer upgrade anyway (or perhaps a Hammer if AMD gets them out in time and they can be cooled ok), but it seems unfortunate that AMD doesn't provide much competition in this regard.