Test Setup & Measurement Methods
Why Do We Test Each Paste In Four Scenarios?
In choosing four test platforms, we incorporated feedback from our valued readers. For instance, you wanted to see us take the cooler mounting pressure into account. We're skipping the LN2-based testing and focusing on scenarios you'll encounter in the real world. For example, we're using popular pre-assembled water coolers that should ensure heat sink temperatures below 60 °C (140 °F), premium aftermarket air coolers with back plates that should demonstrate high mounting pressure, and a run-of-the-mill budget cooler with push-pin mounting (that'll give us limited pressure). Stock coolers like that let the CPU get above 60 °C/140 °F (AMD) and 80 °C/176 °F (Intel).
Depending on viscosity and composition, not all pastes are a good fit for every application, nor are they all well-suited for novices.
The systems we use for CPU measurements haven’t changed since the last time we covered thermal pastes. A quick check showed us that old pastes tested on the latest hardware yield similar results. Moreover, the sensors used in previous-gen CPUs yield more accurate user-facing data than those found in newer processors.
Exact temperatures are measured using a thermal diode under the heat spreader. This is extremely important and essential for an objective evaluation. Using Tcase instead of Tcore is the correct approach to take.
It is even a little exciting that these test components have lasted so long, even though our CPUs, graphics card, and motherboard were all sitting in storage. The only piece of hardware we swapped out for today's update was the power supply.
|Test System One: Closed-Loop Liquid Cooling|
|Fan||Original H80i fan, powered from an unregulated 7 V supply|
|Motherboard||Asus 990FX Sabertooth|
|Test System Two: Air Cooler with Back Plate (Screwed On)|
|Cooler||be quiet! Shadow Rock|
|Fan||Original Shadow Rock fan, speed set to 70%|
|CPU||Intel Core 2 Quad Q6600 (Q0 Stepping) At 2.66 GHz|
|Test System Three: Intel Boxed Cooler (Mounted with Push Pins)|
|Cooler||Intel Boxed Cooler|
|Fan||Original Intel Fan, Speed set to 80%|
|CPU||Intel Core 2 Duo E6850|
Testing Thermal Paste On A Graphics Card
This is a somewhat sensitive topic, and for safety reasons we excluded electrically conductive or liquid metal pastes from our testing. Since GPUs don’t have a heat spreader, but allow the cooler’s sink to directly sit on the die, I didn't want anyone to risk a short circuit.
We also used an older graphics card, which was convenient to test with. Its cooler was mounted using four screws and its fan speed could be dialed in to a constant value. Furthermore, we figured that an older card would be more tolerant of higher temperatures. After all, we didn't want a cheap paste to destroy an expensive, current-gen board. Fortunately, the GPU die size and surface temperature are still comparable to modern mid-range cards.
|Test System Four: Graphics Card Test|
|Cooler||Zalman GPU cooler|
|Fan||Original Zalman fan, speed set to 80%|
|CPU||AMD Radeon HD 4850|
|Test Environment||Test System 1 (see above)|
Test Cycles, Test Duration & Settings
Because the digital temperature sensors built into modern CPUs only give us uncalibrated Tcore values, as mentioned, we use the old way of measuring die temperature with a thermal diode under the heat spreader. The processors in this story still use soldered-on spreaders, so this value should be fairly accurate. We'll report the difference between Tcase and the room temperature because there are always slight fluctuations in the (air-conditioned) room that could slightly distort the results for Tcase.
For the graphics card, we use the temperature as the GPU reported it. That number isn't influenced by minor changes in room temperature, so long as they stay within 2°C of our 22°C baseline.
|Room Temperature||Approx. 22°C (relatively constant from 21.4 to 22.7°C)|
|CPU Test Results||Reported in °C as an average of temperature differences (Difference between the ambient temperature and the reading of the sensor under the heat spreader)|
|GPU Test Results||Output in °C for the GPU diode|
|Test Cycles CPU||1x four-hour burn-in, followed by break of at least two hours 4x one-hour measurement, with one-hour breaks Total time at least 16 hours per thermal product and cooler|
|Test Cycles GPU||1x four-hour burn-in, followed by break of at least two hours 2x one-hour measurement, with 30 minute breaks Total time at least 8.5 hours per thermal product|
Comparison Thermal Pastes
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