We place our test rigs under load using the Small FFTs stress test in the free application Prime95, as this test is designed to place maximum load on the CPU and minimum load on the system's memory. We use the freeware application Core Temp to measure the temperature of our CPUs, as it reads data from the DTS (digital thermal sensor) embedded inside each core of Intel's modern processors and thus provides as accurate a reading as possible. We always take the temperature of the hottest core for consistency, and do so after 15 minutes of the Prime95 test, which is enough time for temperatures to plateau.
The results provided are the delta T results; the difference between the recorded CPU temperature and ambient temperature at the time of testing. Our labs are not temperature controlled, so this provides the most accurate method of comparison for coolers tested on different days.
We used a de-lidded Core i5-3570K, which has improved the thermal contact between the CPU core and heat spreader, applying Coollaboratory Liquid Pro thermal paste throughout testing, and applying the included thermal paste of the AIZ77ITXD to the chipset.
Intel LGA1155 Test System
De-lidded Intel Core i5-3570K overclocked to 4.4GHz (44 x 100MHz) using a vcore of 1.3V