Air Cooler Shoot-Out

Review by Doug Horton. With continuing interest in overclocking, which is usually best done with third-party CPU cooling, I was provided an opportunity to test Corsair’s A70 High Performance CPU Cooler, and I compared its performance with the Coolermaster Hyper 212 EVO product, which is an improved version of the popular Hyper 212 Plus product I’ve previously reviewed and which provided great performance results at a budget price.

Corsair A70 Air Cooler

The Corsair model A70 is a robust air cooling product, with lots of heat transfer surface in the finned heatsink. It’s furnished with matching inlet and outlet fans, each with two selectable fan speeds; and it’s designed to have lots of surface contact between the four heat pipes and the top surface of the CPU, using the partially-flattened heatpipe method.

Retail package for Corsair A70 CPU cooler

The A70’s method of providing direct contact between the heat pipes and CPU is similar to that found in the previously reviewed Coolermaster Hyper 212 Plus product. Note that the A70 is the “big brother” of the Corsair A50 air cooler, which is furnished with one fan, a slightly smaller heat sink, and three instead of four heat pipes.

Corsair A70 heatsink with four heatpipes and two fans

A70 Installation

Installation was not as straightforward as I hoped. Because of the heatsink size, particularly depth, and with its overhang on the inlet-side fan, I had to install two short height memory sticks, instead of using memory with larger heat spreaders, such as the Corsair Dominator and Vengeance products that I’ve previously reviewed.

The directions for installation with both Intel and AMD processors are adequate, but they are incomplete for the Intel installation I tested. Specifically, there are two sets of parts that are not shown or mentioned in the instructions: four small screws that can be used to secure the H-shaped mounting bracket to the heat sink block for the Intel installation, and four small fiber washers that could be used under the aforementioned screws or under the screw knobs that tighten the heatsink to the cooler’s backplate. However, if used under the latter, the mounting bracket would be pushed more toward the processor and motherboard on all four corners, perhaps more than intended.

The mounting system is quick and easy, assuming the user has easy access to the underside of the processor area of the motherboard. After the processor is installed, for the Intel installation, four long thin bolts are first attached to socket-applicable positions on the four arms of the backplate. After the backplate is correctly aligned, the four bolts are then pushed through the four corresponding cooler mounting holes in the motherboard. Next, the H-shaped bracket is inserted below the heatsink fins and screwed to the top of the heatsink contact block.

After a small amount of thermal paste is applied thinly to the heatpipes, as shown in the accompanying image provided by Corsair, the H-shaped bracket and heatsink are lowered onto the four threaded bolts, and then the furnished screw knobs are placed over the four thin bolts and tightened until they are “finger tight.” The AMD installation is much simpler, as only the furnished cam-tightened mounting arm is used, without using any of the other parts.

Application of thermal compound to contact area of A70 heatpipes

Though possibly not important to its performance, the A70 heatsink is not symmetric on the sides to which the fans are attached, as viewed looking downward. One side is clearly concave, curved inward about 5 mm, and the other side is flatter and slightly W-shaped.

It’s not clear in the instructions for users, how the heatsink should be aligned with the processor and motherboard, and to which sides of the heat exchanger the fans should be attached. Though not explained in the user instructions, the proper assembly was explained in the Reviewers Guide I received from Corsair.

I’ve subsequently suggested to Corsair that the latter should be renamed and provided as the user guide.

The two furnished fans are already attached to mounting shrouds, with one fan mounted to its shroud for pushing air into the heatsink. The other fan is pre-mounted to its shroud for pulling air out of the heatsink, though this can only be discerned by viewing small black-on-black arrows on the fans, which indicate airflow directions.

On the Intel DP67BG motherboard I used for this testing, I chose to attach the fans to move air toward the back of the motherboard and case, as is usually customary. On the air inlet side, this causes air to be drawn over the tops of the memory sticks, and on the outlet side, air is blown over small heat sinks on the motherboard between the processor and the motherboard’s external connectors.

A70 Fans Speeds and Sound Levels

The A70 is provided with two two-speed fans, with 3-pin connectors. If the fans are connected directly to the motherboard, they are rated for 2000 rpm and a sound level of 31.5 dBA. If connected with the furnished inline resistor/connectors, they are rated for 1600 rpm and a sound level of 26 dBA. This contrasts with the price-comparable CoolerMaster Hyper 212 EVO, which is furnished with one 4-pin PWM (variable speed) fan that is controlled by the motherboard to run at 600-2000 rpm, with sound level at 9 to 36 dBA.

Detail of fan mounting to shroud, showing rubber sound isolator

For operation at low cooling demand, with lower sound level, I prefer the PWM fan approach; however, even if operated at the 2000 rpm speed, the A70 fans are still extremely quiet, in part because they are attached to their shrouds with rubber sound isolating mounts, as shown in accompanying image from Corsair.

Coolermaster Hyper 212 EVO Air Cooler

This cooler is very similar to the Corsair A70 cooler, with four principal differences:

• The EVO heatsink is physically smaller than the A70 cooler, by about 25%.
• The EVO cooler is furnished with only one fan, compared to two fans with the A70 model, though the package includes extra fan mounting brackets for adding a second fan.
• The EVO fan is a 4-pin PWM type, with variable speed that can be controlled by the motherboard.

The heat pipes, where they contact the processor top surface, are flatter on the EVO product and the heat contact surface is greater – a technology Coolermaster calls “Continuous Direct Contact.” This feature sets the Hyper 212 EVO model apart from its Hyper 212 Plus predecessor, as well as from the A70 cooler. See comparative images of contact areas below.

Coolermaster Hyper 212 EVO Fan and Heatsink

Corsair A70 processor contact area

Hyper 212 EVO processor contact area

Comparative Air Cooler Specifications

Here are specifications of the Corsair A70 and Coolermaster Hyper 212 EVO air coolers:

*maximum dimensions, measured by author in three directions, without fans

Cooling Efficiency Comparison

I compared the Corsair A70 and Coolermaster Hyper 212 EVO air coolers with repeated, identical measurements of processor temperature at 100% processor load. I ran the tests using Intel’s Extreme Tuning Utility, which provides for processor adjustments and monitoring of many parameters, including core utilization and temperature, as well as providing a stress test.

My test system configuration included an Intel DP67BG motherboard and i5-2500K processor, overclocked to 4.0 GHz, with 2 x 2 = 4 GB of Corsair XMS memory, operated at rated 1600 MHz. The graphics card was an EVGA GTX 460 SC, though this has no relation to processor cooling efficiency.

I ran the Corsair A70 cooler with both inlet and outlet fans attached, at both 1600 and 2000 rpm settings. In both tests, the maximum temperature observed was 87°C. I then changed the cooler to a Coolermaster Hyper 212 EVO. The EVO fan remained at about 610 rpm during the 100% processor load test, and the maximum temperature observed was 68°C. Though both 87°C and 68°C are both safe temperatures for processor operation, running with lower temperatures is likely better over the life of the processor.

It’s not clear why the Corsair A70 cooler with larger heatsink size, larger diameter heat pipes, and double the number of fans is less efficient than the Coolermaster EVO cooler, though the difference might be explained by any or all of the following thermodynamic and fluid-dynamics issues:

• The heatsink to processor contact area is greater for the Hyper 212 EVO than the A70, which might more than make up for the A70’s larger heatsink and double fans.
• Given that running the Corsair fans at both 1600 and 2000 rpm led to the same processor temperature, there may be a maximum amount of air that can smoothly flow between the heatsink fins, based on the horizontal areas and vertical spacing. It’s possible that too much air is being provided and not moving smoothly between the fins, perhaps because of turbulence and/or frictional resistance to flow.
• Because the two A70 fans are not electrically synchronized, the outlet fan blades may be aerodynamically blocking exiting airflow from the inlet fan, causing an overall reduction of airflow through the heatsink.

Summary

The Corsair A70 cooler is impressive in size, design, and packaging. On the other hand, in my limited testing, it did not perform as well as the lower priced, competitive Coolermaster Hyper 212 EVO product, most likely because of aerodynamic issues with moving air through the heatpipe and fin heat exchanger.

The EVO remains my recommended product for replacing default CPU air coolers with more robust air coolers.

At time of writing, the A70 was declining in availability, and the EVO was selling for about $40, from popular online retailers, though discounts and rebates are often available. Perhaps the “free market” has made a choice in favor of the better performing product.