Methodology and Test Results

Heatsink Test Methodology

Benchmark Reviews has solicited suggestions from the enthusiast community, and received guidance from some of the most technical overclockers on the planet. As a result, our testing methodology has been refined with every new project. Because of this, each article is really its own stand-alone product, and cannot be fairly compared to the others. This particular article is a perfect example of that principle, since we’re using a fresh methodology. Benchmark Reviews continues to test CPU coolers using the stock (bundled) fan whenever applicable.

Testing was conducted in a loosely scientific manner. Ambient room temperature levels were maintained within one degree of fluctuation, and measured at static points beside the test equipment with a calibrated digital thermometer. Manufacturer-supplied thermal paste was not used in these tests, and a common Thermal Interface Material of our choosing (listed in the support equipment section below) was utilized instead. The processor received the same amount of thermal paste in every test, which covered the ICH with a thin nearly-transparent layer. The heatsink 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. AIDA64 System Stability Test 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).

Since our test processor reports core temperatures as a whole number and not in fractions, all test results utilize AIDA64 to report averages (within the statistics summary 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.

When each cooler is tested, Benchmark Reviews makes certain to keep the hardware settings identical across the test platform. This enables us to clearly compare the performance of each product under identical conditions. Careful consideration is made so that ambient room temperature does not fluctuate more than 1°C during testing, to ensure that the thermal delta would not change enough to impact our test results. Benchmark Reviews reports the thermal difference in our test result charts. For the purpose of this article, thermal difference (not the same as thermal delta) is calculated by subtracting the ambient room temperature from the recorded CPU temperature.

Intel Test System

• Processor: Intel Core i7-2600K 3.40 GHz (overclocked to 4.0 GHz @ 1.40V)

Benchmark Software

• FinalWire AIDA64 Engineer Edition v5.75

CPU Cooler Test Results

All of the tests in this article have been conducted using vertical motherboard orientation, positioned upright in a traditional tower computer case. At the start of our test period, the test system is powered on and AIDA64 system stability tests are started with Stress CPU and Stress FPU options selected. For a minimum of thirty minutes AIDA64 loads each CPU core to 100% usage, which drives the temperature to its highest point. Finally, once temperatures have sustained a plateau, the ending ambient room temperature and individual CPU core levels are recorded.

Using the bundled Intel LGA1155 cooling solution as a baseline measure of performance, this air-cooled heatsink typically reduced 100%-utilized CPU temperatures to 42.9°C over the ambient room temperature. The remainder of our test coolers were all-in-one liquid cooling solutions, which offer much better thermal management.

The Antec KÜHLER H2O 920 utilizes a 12cm radiator, and can accommodate two cooling fans (included). With one fan attached temperatures hovered at 33.2°C over ambient, but adding a second fan helped reduce that average to 30.7°C over ambient room temps at full load. Next was the Cooler Master MasterLiquid Pro 120, which includes two cooling fans for a 12 CM radiator. This all-in-one liquid cooling solution produced 29.9°C with a single fan attached, and improved to 25.6°C with both fans.

At the top of our thermal performance results were the 24cm radiators, with twice the capacity and cooling surface. These coolers require a case with dual 120mm fan vents for proper fit and operation. Corsair’s H100i V2 comes with two 120mm fans, which were both attached to the radiator. Under full processor load, the Corsair’s H100i V2 averaged 24.3°C over ambient room temperatures. The best performance was achieved with the MasterLiquid Pro 240 cooling solution, which delivered 23.5°C over ambient with both (bundled) 120mm Air Balance fans attached.

Aside from the stock Intel thermal cooling solution, all of the liquid coolers utilized fans that created very little noise and were typically more quiet than the cooler’s pump motor. Although subjective, MasterLiquid Pro’s pump seemed to be nearly silent during operation when listening up close to the waterblock.

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.