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The test bed and a few test tools.
Key Components in Heatsink Test Platform:
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.
4.31, used to monitor the on-chip thermal sensor. This sensor is not
calibrated, so results are not universally applicable; however,
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.
2.01, used to monitor the throttling feature of the CPU to determine
when overheating occurs.
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:
- 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.
- 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.
- 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.
- The fan speed is set to 12V.
- 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.
- 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.
- Thermal rise (?T) is calculated for each voltage level. The formula is Thermal
Rise = CPU Temperature - Ambient Temperature.
- 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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