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Alpha PAL8045

Designed for Socket A exclusively, the Alpha PAL8045 (Dan's reviews are known to give heatsinks a much higher C/W than usual, but he's very accurate. He considers the PAL8045 to be 0.53 C/W) was regarded as the king of all Socket A heatsink coolers, though in its later years upstarts such as the Swiftech MCX 462 and the various all-copper Evercools managed to supplant it - But only with the help of a screamingly loud fan. As far as quiet, efficient heatsinks go, the PAL8045 was not beaten until the heatpiped tower coolers started to appear five years later, such as the Coolermaster further down this page.

The PAL8045 was so efficient that increasing the fan to one with four times the output made very little difference to the effectiveness of the heatsink. Using Alpha's "Microforge" process, the aluminium cooler had, as can be seen, numerous small hexagonal pins instead of the traditional fins or vanes. This gave it a massive surface area and increased its density, both important for a heatsink. This caused a large pressure drop from the top of the heatsink to the bottom which is normally a bad thing. Air couldn't flow as freely through the PAL8045 as it could a traditional cheap fin thing (see the Evercool below for a typical example). This meant the PAL8045 didn't benefit much from very powerful fans, but the trade-off which Alpha hit a perfect sweetspot on was that the PAL8045's surface area was massive. The heatsink didn't have the same kind of airflow as hairdryer emulators but it made much better use of the airflow it did get.

The copper inlay was used for its high thermal conductivity, it spread the heat load across the base of the heatsink so that the outer areas were more effective and the heatsink could be made larger than the typical 60mm. In this case, the heatsink was a full 80mm and one of the first of the 80mm heatsinks which used fans which before then had typically been reserved for case cooling. 80mm fans are able to move more air at a lower RPM rate, so be just as effective at a lower noise level.

Being a bolt-through-holes cooler, the heatsink required a motherboard compliant with AMD's mounting hole specifications which not all of them were. Common designs from Gigabyte, Asus, Abit and DFI were compliant, I used it with an Abit KT7, KT7A, KX7-333 and Asus A7N8X-X, but cheaper boards typically didn't bother - Check the PC Chips/ECS board in the motherboards section, the two mounting holes comply with no known specification.

It cost a fortune, it wouldn't fit all motherboards, it required assembly, it usually didn't come with a fan, but if you could fit it, use it and set it right...oh boy were you in for a treat.

Evercool CUD-725

There are two ways of making a heatsink. You can do the smart way, design a precision made instrument (see the Alpha above) and charge a fortune for it but sit back and know you're putting the newbies in their place. Or you can put together a few fins and a screamingly powerful fan on top (Anyone ever seen an OCZ Dominator? No? Bet you heard it coming, though!) of an otherwise unimpressive heatsink and be guaranteed great performance. Sure, you wouldn't beat the Alphas of the world, but you'd be about half their price.

With a screamingly loud Delta 70mm fan and an all-copper design, the Evercool CUD-725 belongs in the latter category. It's actually heavier than the Alpha PAL8045 (though not by much) but a lot cheaper to make. It's a skived-fin copper thing completely lacking in grace and subtlety. That's not to say it was bad, far from it, but that it wasn't excellent. It performed within a hair of the Alpha PAL8045, but at a much higher noise level.

A simple design, done well, the rulebook followed to the letter. Most testing placed the CUD-725 around the 0.60 C/W level.

Coolermaster Hyper6+

Sat atop an ATX PSU for scale (as are most of the other heatsinks on this page), the Coolermaster Hyper6+ is a six-heatpipe two-stage tower cooler with copper heatpipes and aluminium vanes. In the original Hyper6, the vanes were also copper which added a great deal to the mass of this behemoth, but the aluminium version weighs in at 'only' 971g.

In use, the Hyper6+ was able to keep an estimated 110W load (2.8GHz dual core Opteron at 1.45V) at 65C with the fan turned down to only 80% PWM - From this I work out an excellent real-world thermal resistance of 0.20 - 0.25 C/W. In design, it has a large copper slug on the bottom to make contact and house the hot end of the heatpipes but where most coolers then have a whole load of open space doing nothing, the Hyper6+ fits a first-stage heatsink which cannot harm performance but probably won't make much difference. The aluminium vanes are closely spaced but parallel, well fitted and offer very little resistance to airflow. It's big, effective, imposing, weighs almost a kilogram...and the fan glows blue. What more could one want?

Alas, the universal fitting of the Hyper6+ fits all current (and past) sockets with mounting holes...except Socket F and Socket AM2(+). When I moved to AM2, the Hyper6+ had had to be retired...Until, like with most of my hardware, it found use in this server. Quiet, extremely high performing and reliable. Just what you need in an always-on system.

Other than the lack of AM2 compatibility, the other problem with the Hyper6+ is its use of a non-standard 100mm fan. 92mm and 120mm are standard, but 100mm fans are extremely difficult, almost impossible, to find.
TBC Corsair H80 CLC

CLCs came of age with the advent of very small high pressure pumps and the use of propylene glycol as a coolant. Very quickly models from Fractal Design, Corsair, NZXT, Swiftech, etc. all appeared at very attractive price points. Even AMD got in on the action and began fitting them from the factory to some high end GPUs. Mostly, they were identical and differed in the fans supplied, because they were being made by the same supplier: Asetek. Cooler Master, Apaltek and some others got in on it, but even they largely used the same radiators.

Corsair's H80 runs three profiles, cycleable via a button on the CPU plate, predictably "low", "medium" and "high". The pump, in my case, is silent, but others have reported noise. The fans do not spin down much at all when on medium and high, and always make noise. On high, quite a lot of it, so those who can thermally control their fans are advised to put the pump on full and control the fans themselves.

It is immensely effective. It sustained a full load highly overclocked Phenom II X4 955 BE at 3.8 GHz, which drew an estimated 220 watts, at below 70C.

The advantage of a CLC, indeed any liquid cooler, is that the heatsink or radiator device can be placed out of the way, it's not limited by whatever will fit mounted to the motherboard. This means it can be very big, very heavy and very dense, all highly desirable traits for a heatsink.

Of course, an overclocked Phenom II won't last anyone forever, and it was replaced by a Core i5 2500. The H80 was set on "low", and controlled the fans itself.

Under full load from Prime95 small-FFTs, the Sandy Bridge reported itself as using 76 watts total. This is hardly going to strain anything, so OCCT was brought in. The TDP's 95 watts, let's try to get closer to it? OCCT managed 62 watts and the CPU didn't even break 60C. This became a challenge! Manually limiting OCCT to 4 threads and a small data set got package power up to 76 watts and temperature to 65C, but surely we can do better?

OCCT's AVX capable Linpack came next. AVX is responsible for a lot of power, and we hit 80 watts quite quickly while temperatures stabilised at 70C. I can only assume the thermal interface is rubbish or the H80 needs more pump speed - so it was set to "Medium" while the test was still running. Fans ramped up, pump RPMs (reported via a 3 pin fan connector, a neat touch) ramped up, noise ramped up and... Nothing. Temperature remained flat at 70C, a few flicks to 71C, then power dropped to 48 watts before resuming at 80 watts, ruining the nice flat temperature trace. The temperature made no further threats to reach 70C. Clearly something more reliable a load than OCCT was needed.

IntelBurnTest got to 78 watts but was all over the map. 7Zip's benchmark got to 46 watts and was a bit of a joke, but it's mostly memory bound anyway, and actually scored worse than the peak result I'd seen on the Phenom II X4. Tweaking it to fit the dictionary in L3 cache and running a few more threads helped close in on 50 watts, but this isn't a stress test for thermals. An old favourite was "burnk7", hard to find, and designed to present maximum load to an Athlon back in the day. It was also a very high load for Core and Core 2 processors, but evidently not for Sandy Bridge: Which hit 51 watts only. I then updated Prime96 from 27.9 to 29.4, which is AVX aware. CPU hit 75 watts immediately but went little further, stabilising around 76.5W. I left this going at 64C and ramped the H80 up to "High". Temperature fell slowly to 62C and stayed there. With a resounding "Meh" from this whole round of testing, I set the CLC back to its "Low" profile. Temps very slowly rose back up to around 66C.

The only conclusion is that a low 70-80 watt load just isn't enough to let the Corsair H80 strut its stuff properly.
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