We've included results from several CPU coolers in each test. Not all are present in all socket tests because some aren't compatible. In this case we've tried to include a similar cooler from that particular company, such as the Noctua NH-C12P which is compatible with LGA 775 and Socket AM2+, but not with LGA1366. In this case we've used Noctua's NH-U12P SE 1366.
Where CPU coolers had alternative fan speeds, we've tested at both the lowest and highest fan speed settings and recorded idle and load delta T results for each setting to give you some idea as to how much performance is affected.
We've also included the reference cooler for each socket which is a good indicator of what kind of improvement you'd see when upgrading. For instance, you certainly wouldn't want to buy a third-party cooler that performs worse than the reference cooler.
Delta T is the difference in °C between the ambient temperature and the recorded temperature of the hardware, in this case the CPU. We used Core Temp 0.99.4 to take temperature readings of the CPU from the Digital Thermal Sensor (DTS) embedded in the core of every modern CPU, at idle and under load while using the smallfft test in Prime95.
A multimeter thermal attachment probe was used to take the ambient air temperature three inches away from the case's primary intake location. The delta T is a more accurate and comparable method of recording temperature because the ambient room temperature of our test lab fluctuates from day to day.
For Socket AM2+ we used a 3GHz AMD Phenom II X4 940 Black Edition overclocked to 3.6GHz with the vcore boosted to 1.6V. Our LGA775 coolers had to contend with a 2.13GHz Xeon X3210 overclocked to 2.66 GHz by increasing its FSB from 266MHz to 333MHz and increasing the vcore to 1.41V. Our LGA1156 rig is built around an Intel Core i7-870 overclocked to 3.6GHz with a vcore 1.35V. Finally, the LGA1366 test rig used a 3.2GHz Core i7-965 Extreme Edition overclocked to 3.6GHz with a vcore of 1.3V.