CPU Cooler Testing Methodology
Benchmark Reviews is always looking to improve our testing methodology over the past few years. We have always solicited suggestions from the enthusiast community, and received guidance from the experts in this field. This particular time we will be using a fresh testing methodology. Benchmark Reviews continues to test CPU coolers using the stock included fan and thermal interface material (whenever applicable), and then replace it with a high-output fan and aftermarket TIM.
Manufacturers are not expected to enjoy this sort of comparison, since we level the playing field for all coolers by replacing their included fan and TIM with common units which are then used for every CPU cooler tested. Many manufacturers include fans with their heatsink products, but most ‘stock’ fans are high-RPM units that offer great airflow at the expense of obnoxiously loud noise levels. By using the same model of cooling fan and TIM throughout our second test, we can assure our results are comparable across the board. This is one of the more significant changes we have made to our test methodology, since many of the benchmark tests we have conducted in the past have compared the total package. Ultimately we’re more interested in the discovering the best possible cooler, and we believe that you’ll feel the same way.
Motherboard: Asus Gryphon Z87 Motherboard
Processor: Intel Core I5 4670k
Enclosure: Phanteks Enthoo Mini XL
Operating System: Windows 7 Professional.
Testing was conducted in a loosely scientific manner. Ambient room temperature levels were maintained within one degree of fluctuation, and measured at all times throughout testing. The processor received the same amount of thermal paste in every test, which covered the ICH with a thin nearly-transparent layer. The cooler being tested was then laid down flat onto the CPU, and compressed to the motherboard using the supplied retaining mechanism. If the mounting mechanism used only two point of force, they were tightened in alternation; standard clip-style mounting with four securing points were compressed using the cross-over method. Once installed, the system was tested for a baseline reading prior to testing.
At the start of each test, the ambient room temperature was measured to track any fluctuation throughout the testing period using Asus AI Suite and two of the included temperature sensors located at the front intake of our test system. Aida 64 Engineer was utilized to create 100% CPU-core loads and measure each individual processor core temperatures. It’s important to note that software-based temperature reading reflects the thermal output as reported from the CPU to the BIOS. For this reason, it is critically important (for us) to use the exact same software and BIOS versions throughout the entire test cycle, or the results will be incomparable. All of the units compared in our results were tested on the same motherboard using the same BIOS and software, with only the CPU-cooler product changing in each test. These readings are neither absolute nor calibrated, since every BIOS is programmed differently. Nevertheless, all results are still comparable and relative to each products in our test bed (see The Accuracy Myth section below).
All test results utilize Aida 64 Engineer to report core temperature averages (within the statistics panel), which gives us more precise readings. To further compensate for this, our tests were conducted several times after complete power down thermal cycles. Conversely, the ambient room temperature levels were all recorded and accurate to one-tenth of a degree Celsius at the time of data collection.
The Accuracy Myth
All modern processors incorporate an internal thermal diode that can be read by the motherboards’ BIOS. While this diode and the motherboard are not calibrated and therefore may not display the actual true temperature, the degree of accuracy is constant. This means that if the diode reports 40°C when it’s actually 43°C, then it will also report 60°C when it’s truly 63°C. Since the design goal of any thermal solution is to keep the CPU core within allowable temperatures, a processor’s internal diode is the most valid means of comparison between different heatsinks, or thermal compounds. The diode and motherboard may be incorrect by a small margin in relation to an actual calibrated temperature sensor, but they will be consistent in their margin of error every time.