In the quest to build a better heatsink manufacturers have become incredibly creative. Take the Auras CTC-868 heatsink Frostytech is reviewing for you today for example. The heatsink features twin 92mm fans set up in a push-pull configuration, on dual pivoting supports the user can move and adjust. The stated goal of the Auras CTC-868 heatsink is to exceed stock Intel CPU cooler performance while maintaining a low noise output - the design is a rare and unique approach to that end.
What makes the Auras CTC-868 heatsink stand out is that it's split into thirds, with the two outer sections holding the integrated fans. A slip connection at the base of the CTC-868 allows each outer third of the heatsink to pivot on the connecting heatpipe 20 degrees, in the process noise is slightly reduced and the exhaust airflow can be directed down towards the motherboard.
The Auras CTC-868 heatsink is vaguely reminiscent of the Zalman CNPS9700NT in shape, but the two slip connections that allow the heatpipes to rotate freely make us concerned about thermal joint resistance affecting thermal conductivity in a negative fashion. Both 92mm fans in the CTC-868 are internally illuminated with blue LEDs for visual impact. One fan is PWM and rotates at 800-2400RPM, the other spins at a fixed 1200RPM, a single 4-pin cable supplies power to the heatsink.
According to Frostytech's real world sound measurements, the Auras CTC-868 generates between 46.2 - 48.7dBA noise depending on the positioning of each wing. The entire heatsink is chrome plated, and all joints are soldered, except for the two outer wings which pivot on the heatpipe threading through the base. The fins of the heatsink are radially shaped, and connected to the base by one or two heatpipes. The Auras CTC-868 weighs about 568 grams, and comes with two mounting brackets for Intel Core 2 Duo/Quad/Extreme and AMD Athlon64 processors, and a small syringe of thermal compound.
At first glance the Auras CTC-868 is fairly unremarkable, but closer examination reveals a few hidden attributes Frostytech has not seen employed on any other heatsink before. Whether these moveable wings allow the CTC-868 to gain a performance edge... we'll leave until we come to the thermal test results.
Here is the Auras CTC-868 shown completely open for clarity. In practice the heatsink's 'wings' cannot be opened this far because the CPU socket mounting clips get in the way. At the center you can see the three notches which correspond to a wing position of closed, open 1 notch, and open 2 notches.
The central portion of the Auras CTC-868 is just cooling fin, the fans are located on the outer two wings.
In practice Frostytech found the best thermal results were with the wings close, and the lowest noise when they were opened to the 2nd notch. Two finger tabs at the top of each wing (top right, image below) allow quick adjustments without the need for tools.
Base Finish and Flatness
Flipping a heatsink over to inspect the business end is often a simple indicator of overall cooler quality. More practically speaking, a heatsink is in many ways only as effective as the contact it makes with the processor - the flatter and smoother the better. Base finish is one of the criteria that Frostytech measure in the course of evaluating heatsinks, and it involves two distinct aspects. Surface Finish is the first; this is calculated with the aid of Surface Roughness Comparator that has a cross section of common machine surface finishes and their numerical surface roughness equivalents in microinches. The second is Surface Flatness. This is tested with an engineers straight edge or proven flat surface, in two axis.
The copper base of the Auras CTC-868 heatsink has a machined and polished surface texture. Surface roughness is at or better than ~8 microinches, which is considered excellent. The base is roughly 3.5mm thick over the heatpipes and generally flat in both axis. The edges are slightly raised in one direction, giving it a very slight convex appearance when examined with an engineers straight edge. A screw hole at each corner allows the different socket mounting brackets to be installed with a couple screws.
FrostyTech's Test Methodologies are outlined in detail here if you care to know what equipment is used, and the parameters under which the tests are conducted. Now let's move forward and take a closer look at this heatsink, its acoustic characteristics, and of course its performance in the thermal tests!
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