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Cooling System and Noise

The DirectCU II cooling system is the key feature of this graphics card from ASUS.

It consists of five copper heat pipes, two heatsinks and a metallic casing with fans. Two out of the five pipes are 8 millimeters in diameter. The other three are 7 millimeters.

The plate on the reverse side of the PCB merely serves for decoration or protection but doesn’t act like a heat-spreader.

There is an additional aluminum heatsink with thermal pad on the power circuit components. There are 0.5mm aluminum fins press-fitted on the heat pipes with a step of 1.8 millimeters. The two heatsinks are roughly similar (52 and 48 fins).

The cooler’s sole features direct-touch technology. The 2mm gaps between the pipes are filled in with an aluminum insert.

The surface of the cooler’s sole isn’t finished well but that’s not as critical for Nvidia’s GPUs that have a heat-spreader as for AMD’s open-die GPUs.

There is a separate metallic frame with two 9-blade 100mm fans (their impellers are 95 millimeters in diameter). The fans are 20 mm deep.

That’s why the cooler and the graphics card at large are so thick.

The fans are PWM-regulated within a speed range of 1000 to 3400 RPM.

We checked out the card’s temperature while running Aliens vs. Predator (2010) in five cycles at the highest settings (2560x1600, with 16x anisotropic filtering and 4x antialiasing). We used MSI Afterburner 2.2.0 Beta 12 and GPU-Z 0.5.9 as monitoring tools. This test was carried out with a closed system case at an ambient temperature of 26°C. We didn’t change the card’s default thermal interface.

Let’s see how efficient the DirectCU II cooler is with its fans regulated automatically and at their maximum speed:


Automatic fan mode

Maximum fan rotation speed

The cooler’s performance is simply amazing. The peak GPU temperature is only 58°C, the two fans rotating no faster than 1320 RPM! Of course, the fans are absolutely silent at such a low speed even against the background of our very quiet PC configuration. Yes, we guess such temperatures are worth the three expansion slots on your mainboard you have to give up to use that cooler. When the fans were rotating at their maximum speed of 3400 RPM, the GPU was no hotter than 46°C. With such a highly efficient and quiet cooler, why didn’t ASUS pre-overclock this card? Did they leave this pleasure for us to enjoy? Let’s first see how noisy the DirectCU II cooler is.

We measured the level of noise using an electronic noise-level meter CENTER-321 in a closed and quiet room about 20 sq. meters large. The noise-level meter was set on a tripod at a distance of 15 centimeters from the graphics card which was installed on an open testbed. The mainboard with the graphics card was placed at an edge of a desk on a foam-rubber tray.

The bottom limit of our noise-level meter is 29.8 dBA whereas the subjectively comfortable (not low, but comfortable) level of noise when measured from that distance is about 36 dBA. The speed of the graphics card’s fans was being adjusted by means of a controller that changed the supply voltage in steps of 0.5 V. We’ve included the results of the Sapphire Radeon HD 6970 Dual Fan, the quietest card with an original cooler we’ve tested so far, into the next diagram. Here are the results (the vertical dotted lines indicate the top speed of the fans in automatic regulation mode):

The ASUS DirectCU II beats one of the best original graphics card coolers we’ve ever tested! Its noise level graph goes lower than that of the Sapphire Dual Fan (Dual-X). Moreover, the top noise level of the ASUS cooler in automatic fan regulation mode is only 33 dBA at 1320 RPM whereas the Sapphire’s top noise is 53 dBA at 2580 RPM. Of course, the low GPU voltage of the ASUS card contributes to this excellent performance. The difference is huge and justifies the triple-slot design of the ASUS GTX 560 Ti 448 cores DirectCU II. We only wonder if the DirectCU II can beat the recognized leader among air-based GPU coolers Arctic Accelero Xtreme, but we will check this out in an upcoming review.

 
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