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[nextpage title=”Introduction”]

The thermal compound, also known as thermal grease, is a key component to get the best cooling performance for your CPU. But are certain products better than others? In order to check this out, we tested thermal compounds from five different brands: Zalman, Prolimatech, Cooler Master, Evercool, and Spire. Let’s see what we’ve learned from this round-up.

For a better understanding on how the thermal compound works and how to correctly apply it, please read our How to Correctly Apply Thermal Grease tutorial. The most important thing that you have to have in mind is that it is a mistake to think that the more thermal grease you apply, the better. The thermal compound is a worse heat conductor than copper and aluminum (the metals usually found on cooler bases). So, if you apply more thermal compound than necessary it will actually lower the cooling performance instead of improving it.

In this roundup we are testing five different thermal compounds, shown in Figure 1.

Thermal CompoundsFigure 1: The thermal compounds included in our roundup

Let’s get a closer look at the contenders in the next pages.

[nextpage title=”The Thermal Compounds”]

Our first contender is the Zalman ZM-STG2 thermal grease, shown in Figure 2. It is the thermal compound that comes with the Zalman CNPS9900 MAX and most coolers from Zalman. It is a gray compound.

Zalman Thermal CompoundFigure 2: Zalman ZM-STG2

In Figure 3, you can see our second contender, the Prolimatech Thermal Grease, which comes with the Prolimatech Megahalems Rev. B and with other CPU coolers from Prolimatech. It is also gray.

Prolimatech Thermal CompoundFigure 3: Prolimatech thermal compound

In Figure 4, you check our third contender, the Cooler Master "thermal compound kit", the gray thermal grease that comes with the Cooler Master Hyper TX3 and other CPU coolers from the same manufacturer.

Cooler Master Thermal CompoundFigure 4: Cooler Master thermal compound kit

[nextpage title=”The Thermal Compounds (Cont’d)”]

Our fourth contender is the Evercool EC420-TU15, a white thermal compound that comes with the Evercool HPH-9525EA CPU cooler. In Figure 6, you can check the other side of the tube, where you will find some data about the product.

Evercool Thermal CompoundFigure 5: Evercool EC420-TU15

Evercool Thermal CompoundFigure 6: Evercool EC420-TU15

Finally, in Figure 7, you can check our last contender, the Spire Bluefrost thermal compound, which comes with the Spire TherMax Eclipse II CPU cooler. In Figure 8, you can see the technical characteristics of the product. This thermal grease is blue, hence its name.

Spire Thermal CompoundFigure 7: Spire Bluefrost

Spire Thermal CompoundFigure 8: Spire Bluefrost

[nextpage title=”How We Tested”]

We tested the thermal compounds using the same testbed system that we currently use to test CPU coolers, which is fully described below. Our Core i7-860 (quad-core, 2.8 GHz) CPU, which is a socket LGA1156 processor with a 95 W TDP (Thermal Design Power), was overclocked to 3.3 GHz (150 MHz base clock and 22x multiplier), and we kept the standard core voltage (Vcore). We used a Zalman CNPS9900 MAX CPU cooler, and the only different part in each test was the thermal compound itself.

We measured temperature with the CPU under full load. In order to get 100% CPU usage in all threads, we ran Prime 95 25.11 (in this version, the software uses all available threads) with the "In-place Large FFTs" option. For each test, we applyied the same quantity of thermal compound (about the size of a grain of rice) at the center of the CPU, as shown in Figure 9.

Thermal CompoundsFigure 9: Applying thermal compound

After each test, we check the base of the cooler, making sure the quantity of thermal compound was optimal. The thermal compound must spread evenly on the metallic part of the CPU, without exceeding it, creating a thin layer. The "fingerprint" shown in Figure 10 shows that the compound was properly applied.

Thermal CompoundsFigure 10: CPU "fingerprint", showing the thermal compound was correctly applied

Room temperature measurements were taken with a digital thermometer. The core temperature was read with the SpeedFan program (available from the CPU thermal sensors), using an arithmetic average of the core temperature readings. During the tests, the left panel of the case was open.

Hardware Configuration

Operating System Configuration

  • Windows 7 Home Premium 64 bit

Software Used

Error Margin

Since both room temperature and core temperature readings have 1 °C resolution, we adopted a 2 °C error margin, meaning temperature differences below 2 °C are considered irrelevant.

[nextpage title=”Our Tests”]

The table below presents the results of our measurements.

Thermal Compound Room Temp. Core Temp. Differerence
Zalman ZM-STG2 24 °C 59 °C 35 °C
Prolimatech Thermal Compound 24 °C 56 °C 32 °C
Cooler Master Thermal Compound Kit 23 °C 58 °C 35 °C
Evercool EC420-TU15 22 °C 57 °C 35 °C
Spire Bluefrost 22 °C 58 °C 36 °C

In the graph below, at full load you can see how many degrees Celsius hotter the CPU core is than the air outside the case. The lower this difference, the better is the performance of the thermal compound.

Thermal Compounds

[nextpage title=”Conclusions”]

Our results are crystal clear: at least with the five brands we included in our roundup, the thermal compound has minimal impact in cooling performance. We tested only five different products (which really is a small sample), but the results were consistent.

From the five thermal compounds we tested, four of them shown practically the same performance. Only the Prolimatech compound behaved differently, but the difference was of only three Celsius degrees, just one degree above our error margin.

We will soon test more thermal compounds and see if the picture is the same. Hang on!