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Date |
: May 7th, 2002 |
| Category |
: Cooling |
| Manufacturer |
: Arkua |
| Author |
: Jin-Wei Tioh |
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These graphs show the temperature delta between the CPU case temperature and the intake air temperature. To maximize CPU power dissipation, we ran StabilityTest, HotCPU Lite and the BlueSmoke RC5-64 Client simultaneously under Windows 2000. The test unit basically consisted of an AMD Duron 800, AOpen AK73 Pro (A) (courtesy of AOpen), a S3 Virge PCI sitting in the last PCI slot and the measuring apparatus (courtesy of HighSpeed PC). The unit was setup on an open tabletop, giving the cooler an ideal functioning environment (ie. unobstructed airflow, minimized recycling of hot air). Air turbulence in the room was virtually non-existant, ensuring that only the fan on the heatsink was doing all the work. Other heat sources (eg. lights, monitors) were also minimized to ensure a more accurate determination of performance results. About the only confounding factor is the heat generated by some of the nearby components, eg. RAM, voltage regulators and the north bridge. Lastly, the primary TIM (thermal interface material) used in the evaluations is Arctic Silver II, kindly supplied by Arctic Silver LLC.
This graph shows the thermal resistance (°C/W) for the heatsinks under each condition. °C/W is both a portable & reliable measurement due to it's dependence on only the temperature delta between the CPU case and the intake air. While absolute temperatures may vary from place to place, you would only need a pair of thermometers that agree with each other to obtain a reasonably accurate °C/W value. To calculate the °C/W of a cooling solution :
°C/W = [CPU Temperature (°C) - Intake Air Temperature (°C)] ÷ Watts
The result would usually fall in the range of 0.2 - 1.5, the lower the better as we'll shortly see why. A rough temperature measurement shouldn't be too difficult for anyone, but obtaining the power dissipation for your CPU (Watts) might present some difficulties). Fortunately, Chris Hare has compiled all the necessary information for nearly all CPU types. All fine if your CPU is running at stock speed and voltage. But what if you overclocked it? No problem, just use :
OC'ed Power (Watts) = Stock Power (Watts) * [(OC'ed Speed (MHz) ÷ Stock Speed (MHz)) * (OC'ed Voltage ÷ Stock Voltage)^2)]
The lower the °C/W, the better? Given the °C/W for a heatsink/fan, you can calculate how well it should work in your system via the following formula :
CPU Temperature (100% Load) = Intake Air Temperature + (°C/W x Watts)
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