Review: Heavyweight P4 Heatsink Roundup

Cooling
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Dec 4, 2002 by Mike Chin

Our first review of P4 (Socket 478) heatsinks has turned into a roundup, like our first review of AMD Socket-A heatsinks. (That's what comes of not publishing a review as soon as it is done.) Also like the first Socket-A roundup, the P4 heatsinks examined here include one lightweight among heavyweights; in this case, the stock heatsink that Intel bundles with its retail P4s. The Intel HSF is a good baseline reference for gauging P4 heatsink performance. At least, it tells us what Intel thinks the minimum requirement is.

The other contenders are the Zalman 6500Cu-B and 6500AlCu-B, the Thermalright AX-478 and the OCZ Eliminator. The Zalman models are the largest "flower" heatsinks in their current lineup, each with over 3300 square centimeters of radiating surface. One has mostly aluminum fins with a small number of copper fins in the center; the other is their top-of-line all-copper model. The AX-478 is a simple adaptation of their very successful AX7 design. They have retained the aluminum fin portion of the AX7 and bonded it to a heavy copper base that fits the P4-478 socket. The Eliminator is a high quality, all-copper skived HS with a low profile that comes with a custom motherboard back support plate.

Our standard low-noise, low-airflow HS testing methodology is used. The same quiet Panaflo low airflow fan is used, at 12, 7 and 5V, with each heatsink. The only variable is the cooling power of the HS itself; we're not comparing fans.

There is one exception: the Intel HS. Why? Because it is an integrated HS + fan design, and the fan is actually thermally controlled. You'll see.

Please read the caveats about P4 thermal diode accuracy on page 2 of the HS test methodology article. There is evidence to indicate the diode might read more than 10° C lower than actual core temperatures. At this time, we use the thermal diode to obtain CPU temperature information. Other options, such as Intel's P4 Thermal Test Vehicle (discussed in this Intel PDF document), are still being investigated.

In the meanwhile, rest assured that our results are as accurate as 99% of HS reviews by other hardware web sites. For those interested in the performance of quality heatsinks when used with a very quiet fan, there is no alternative source of information we know of.

Enough qualifiers already! Let's move on to the review, starting with the Intel HSF.

Product Stock Intel P4 HSF
Market Price Supplied with all retail P4 CPUs; different HSF may be bundled depending on processor speed and/or release date/area.

Intel bundles the integrated heatsink-fan shown on the left below with most of its P4-478 models. There may be other variants, like the one on the right, but this appears to be the most commonly bundled unit. It is a good sized, one piece, all-aluminum unit with a reasonably thick base and fins that are not space too closely. The heatsink (aluminum chunk only) weighs around 300 grams, and the finish is OK, but not up the level of mid-priced (US$25~40) retail alternatives.

There is a thermal interface pad, consisting of a thin square of aluminum with black thermal good on either side, that is attached to the bottom: thermal wax, then aluminum, then more thermal wax! It seems designed to maximize the losses between heatsink and CPU care, especially when you consider that the heat spreader on the P4 already has an extra layer of TIM and aluminum.

It was a pain to get it off. Lots of elbow grease under the tap with baking soda, detergent, warm water and (non-scratch) pot scrubbers. Finally, an alcohol rubdown. Sheesh, millionaire athletes don't have it this good!

More info about this heatsink can be found in the P4-1.6A system silencing project. One important point mentioned on that article is about the mounting clip for this HSF. It exerts a great deal of pressure on the CPU, enough so that the motherboard is actually bowed beneath the CPU. This appears to be a deliberate part of Intel's design, but the Intel HSF causes more bowing than any of the other HS tried so far. The extra pressure likely helps its cooling performance.

AS mentioned in the introduction, the ~60mm fan on this heatsinks is actually thermally controlled. It has a thermistor built in the center rotor area that shifts the fan speed up as it gets hotter. Because the Intel HSF is built as an integrated HSF, it will be tested both with its own fan and with a Panaflo -- the latter setup is shown below.

The photo on the left shows the near 1" gap that resulted from the Panaflo adaptation. To ensure that the Panaflo would deliver its airflow as if mounted right on top of the HS fins as with the other HS, good old duct tape was used to block the gap, as shown on left. The adapted mount also did not put quite as much pressure between HS and CPU as the stock Intel HSF. Still, it seemed plenty tight.

> Zalman 6500B-Cu and 6500B-AlCu

> Thermalright AX478

> OCZ Technology Eliminator

> Testing and Conclusions



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