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Date |
: Aug 22nd, 2001 |
| Category |
: Cooling |
| Manufacturer |
: Various |
| Author |
: Jin-Wei Tioh |
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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)
Thus, the Thermalright SK6 with Arctic Silver II, having a °C/W of 0.28 would keep say a Thunderbird 1.4GHz (72W) at 20.16°C above intake air temperature under 100% load conditions.
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