SPCR's 2010 CPU Heatsink Test Platform [Updates: 10 April & 31 May]

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SPCR's Updated CPU Heatsink Test Platform

January 25, 2010 by Lawrence Lee & Mike Chin

POSTSCRIPT 2: TEST PLATFORM FOR SMALLER HEATSINKS
31 May 2010 - see page 6

POSTSCRIPT: O THE TESTING LIFE!
10 April 2010 - Motherboard replaced - see page 5

For many of us, the journey into silent computing began with the headaches caused by the rattling and droning of the dreaded stock CPU cooler. Whether you had an Intel or AMD processor, the reference heatsink/fan was guaranteed to be loud and inefficient and suitable replacements were few and hard to come by. It wasn't until Zalman launched their famous 7000 series that an average end-user could actually get better cooling with less generated noise at a reasonable price.

Today the situation is much improved with a wide array of coolers to choose from. Quiet and loud, big and small, extravagant and simple, there is a smorgasbord of heatsinks out there which makes reviewing them as important as ever. With so many choices it's paramount that we be able to judge relative performance as objectively as possible while taking into consideration real life application.

CPU Heatsink Test Platform, 2006-2009

  • Intel Pentium D 950 Presler core, C1 stepping. TDP of 95W.
  • Asus P5Q-EM motherboard. A microATX board with integrated graphics and short solid-state capacitors around the CPU socket, and a diminutive northbridge heatsink for maximum compatibility.
  • Intel X25-M 80GB 2.5" solid-state drive.
  • 1GB of Corsair XMS2 DDR2 memory. 2 x 512MB PC2-8500.
  • FSP Zen 300W fanless power supply.
  • Arctic Silver Lumière: Special fast-curing thermal interface material, designed specifically for test labs.
  • Nexus 120 fan (part of our standard testing methodology; used when possible with heatsinks that fit 120x25mm fans)
  • Custom-built, four-channel variable DC power supply, used to regulate the fan speed during the test.

The previous CPU heatsink test board, the Asus P5Q-EM.

Our current CPU heatsink test platform consists of a Pentium D processor on a mATX LGA775 motherboard. A quick-curing thermal compound is used, and if possible, a reference 80/92/120mm Nexus fan. The fan is attached to a custom fan controller to vary the fan speed so we can obtain a good cross-section of performance with regard to airflow and noise. The platform is placed horizontally on a wooden structure, unenclosed. Except for a change in the motherboard last year, our platform has not really changed in several years. With 2010 upon us and the Pentium D 950 passing its 4th birthday, it was decided that the platform was due for an update.

Component Changes?

The Intel Pentium D950 is not as power hungry or hot as today's high-end processors and its die size is smaller. As a result many of the heatsinks we've tested appear to be very close to one another in performance, sometimes making it difficult to conclusively say whether one is superior to another. We also had concerns about the motherboard. Having integrated graphics is convenient for testing purposes, but its VRMs get very hot when placed on load for long periods, and we have to add extra cooling on occasion to avoid testing irregularities which sometimes crop up.

We experimented extensively with a AMD Phenom-II 965 CPU that has a TDP of 125W, with overclocking and overvolting the Pentium D 950 to make it run hotter (over 100W at the AUX12V socket), and with a 130W TDP Intel Core 2 Extreme QX9650 CPU. Many different motherboards were tried during the selection process.

Ultimately we decided to upgrade to a Core i7 setup using the 3.2GHz i7-965 Extreme and an Asus P6T SE motherboard. The i7-965 is one of the fastest desktop processors with a 130W TDP, so it should get heatsinks nice and toasty. The P6T SE has two sets of mounting holes, for both LGA1366 and LGA775 coolers. This means we can use the same platform for LGA1366 heatsinks as well as those with only LGA775 compatibility. The board also has large heatsinks for the VRMs and the NB chip, which bodes well for stability and longevity under high stress.

Surprisingly, the 130W TDP Intel QX9650 drew only 66W at peak load (including losses in the VRM) on the existing Asus P5Q-EM platform — it ran 20W cooler than the old Pentium D 950. (This result was closely matched in a more elaborate test by Lost Circuits.) A Phenom II/AM3 setup was also considered, but rejected in the end due to the extra wear we'd put on the board since the stock retention bracket would have to be removed/reattached often.

i7 represent a maximum of perhaps 10% of Intel's processor sales at this time, a small minority. The i7 processors have been widely recognized as not only the most powerful CPUs, but also the most power hungry. By choosing this processor as the basis of our test platform, we're automatically more focused on cooling very hot processors quietly. This is a tacit recognition that today's typical mainstream processors are no longer a challenge to cool quietly.

Methodology Changes?

We also asked ourselves whether this environment was truly optimal for heatsink testing, after all most systems have the motherboard mounted vertically with the heatsink protruding outward to the side. However, mounting the board in an actual case would increase the wear and tear on the board dramatically, especially since it already is subject to potential damage each time we install a CPU cooler; the methods manufacturers have invented to mount their heatsinks can be scary at times. While replacing a broken board is trivial, SPCR is not an entity with unlimited resources.

It has also been argued that the platform should be enclosed to simulate in-system conditions. If so, other considerations have to be made. What type of enclosure? One with the power supply at the bottom or top? Where should the fan placements and ventilation points be located and what size? Should we add a system fan, and if so, which one, and set at what speed? Going this route may lead to realistic results, but for only one case layout. Also, any extra variables we introduce would benefit some heatsinks while being a detriment to others. For a fair test of heatsink efficiency, we need to eliminate as many performance-affecting variables as possible. For isolating the heatsink, our original, open system setup seems optimal.

Our only change in methodology will be to test high performance heatsinks both with stock CPU settings and overclocked/overvolted. The latter will push the chip's thermal envelope, helping to separate the best coolers from one another.



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