Archive: SPCR's Unique Heatsink Testing Methodology

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Test Platform

The test bed and a few test tools.

Key Components in Heatsink Test Platform:

Test Tools

  • Seasonic Power Angel for measuring AC power at the wall to ensure that the heat output remains consistent.
  • High accuracy Extech MM560 True RMS multimeter & two other multimeters of good precision.
  • High precision LTS 25-NP Current Sensor (to read the AUX12V current), courtesy of Intel. Used in combination with the multimeters to measure the amount of power consumed by the CPU
  • Custom-built, four-channel variable-speed fan controller, used to regulate the fan speed during the test.
  • Bruel & Kjaer (B&K) model 2203 Sound Level Meter. Used to accurately measure noise down to 20 dBA and below.
  • Various other tools for testing fans, as documented in our standard fan testing methodology.

Software Tools

  • SpeedFan 4.31, used to monitor the on-chip thermal sensor. This sensor is not calibrated, so results are not universally applicable; however,
  • CPUBurn P6, used to stress the CPU heavily, generating more heat that most realistic loads. Two instances are used to ensure that both cores are stressed.
  • Throttlewatch 2.01, used to monitor the throttling feature of the CPU to determine when overheating occurs.

Test Procedure

The actual test procedure is quite simple, and can be summed up in a step by step algorithm. The testing takes place twice, once for the stock fan, and again using the reference fan. If there is no stock fan (as is the case for Thermalright's heatsinks), or if the heatsink does not allow for an easy fan swap (such as Zalman's flower heatsinks), one of the tests may be dropped. Common sense rules the roost here; if some part of our methodology that doesn't apply we won't attempt it, but, generally speaking, this is what happens during a test:

  1. Ambient conditions in the lab are measured. Typically, SPCR's sound lab measures 18~19 dBA and 20~21°C. If the ambient conditions stray to far from these norms, testing is halted until they return to normal levels.
  2. The stock fan is removed and profiled according to our standard fan testing methodology, with one important difference: Fan noise (not airflow or RPM) is measured with the fan mounted one the heatsink to better reflect the noise generated by the HSF as a unit, rather than the fan itself. Noise testing is done without the system powered on, leaving the HSF as the only source of noise during testing.
  3. The heatsink is mounted on the test bed using whatever mounting system is available for Intel's Socket 775. About 90% of aftermarket heatsinks have so-called "universal" mounting systems that work with both Intel and AMD-based systems. If we come across an AMD-only heatsink that we just have to review, we may add an AMD-based test bed in the future... or we may attempt to use an adapter to mount it on our existing platform.
  4. The fan speed is set to 12V.
  5. Two instances of CPUBurn (P6) are started and thermal testing begins. The test length is nominally 20 minutes, but no temperatures are recorded until the CPU temperature has been unchanged for at least 10 minutes, verified using SpeedFan's thermal graph (the widest horizontal scale shows roughly 13 minutes of past readings). The P5LD2-VM motherboard exhibits approximately 2~3°C of "jitter" in the thermal readings, so for the purposes of our testing, the "peak" of the jitter is taken as the thermal result.
  6. Steps 4 and 5 are repeated with the fan set to 9V, 7V, and 5V. Lower voltage tests are halted if the CPU begins to throttle, and the heatsink is declared unfit for use at these lower levels of airflow.
  7. Thermal rise (?T) is calculated for each voltage level. The formula is Thermal Rise = CPU Temperature - Ambient Temperature.
  8. Thermal resistance is calculated for each voltage level. The formula is Thermal Resistance = Thermal Rise ÷ 78W (CPU Heat). Thermal resistance is expressed in °C/W, and lower thermal resistance indicates better cooling performance.

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