We measure the CPU temperature of our test rigs when the CPU is idle (Windows desktop) and under load (by running the smallfft test in Prime95). We use the freeware application CoreTemp to measure the temperature of the Intel CPUs, which reads the data from the DTS (digital thermal sensor) embedded in the core of every modern CPU. The DTS gives a far more accurate reading than any third-party temperature sensor, because its readings are not affected by sloppy BIOS programming or a poorly calibrated external health monitoring chip on the motherboard. At the time of testing, only HWMonitor was able to offer readings for our AMD FX CPU.
Because we don't have a temperature control chamber, it's more accurate to measure and quote the delta T (difference) between the ambient and CPU temperature. This means HSFs (heatsinks and fans) that were tested on different days, when the ambient temperature may have varied, can be fairly compared to one another. You'll find the temperature results for the reference HSFs in the graphs. We normally compare the results of each cooler to the reference cooler. However for the Socket AM3+ and LGA2011 systems, we didn't have the reference coolers for these at time of testing so the cooling scores are compared against other coolers rather than how much better the cooler was than the reference cooler.
We've rebuilt our CPU thermal test systems to cater for our current recommended CPU sockets; AMD's Socket AM3 and Intel's LGA1155. While LGA1366 motherboards are still very popular, they've been around for some time and our recommended cooler, the Thermaltake Frio, is still the best option. As Intel's Core i5-2500K and Core i7-2600K CPUs are just as good as all of Intel's LGA1366 CPUs (bar the Core i7-980X Extreme Edition CPUs in a tiny number of situations), LGA1155 is now our main focus, especially as these CPUs run so much cooler.
Socket AM3 test system:
FX-8150 overclocked to 4.4GHz with a vcore of 1.325V
LGA1155 test system:
Core i7-2600K overclocked to 4.1GHz using a vcore of 1.325V
LGA2011 test system:
Core i7-3960X Extreme Edition overclocked to 4.3GHz
using a vcore of1.285V
Each test rig is built inside a SilverStone PS03 midi-tower case and includes an Nvidia GeForce 9600 GT graphics card. The temperatures shown are the delta T between ambient and CPU temperature.