DirectCU II Cooler: Performance and Noise Level
Besides the enhanced power system and pre-overclocked GPU, the ASUS GeForce GTX 660 DirectCU II OC features the exclusive cooler DirectCU II.
It consists of an aluminum heatsink and three 8mm copper heat pipes coated with a nickel alloy.
The heatsink’s base features direct-touch technology with 1.5mm gaps between the pipes.
Its finish quality isn’t perfect, though. The central pipe is the only one to be used 100% whereas the other two get most of the heat through the aluminum insert that fills the gaps between the pipes.
The whole arrangement is cooled by two 75mm fans secured in a metallic frame:
These FirstD FD7010H12S impellers support PWM-based speed regulation:
The speed is varied automatically in a range of 1000 to 3500 RPM. The peak power consumption of each fan is no higher than 4.2 watts. The fans seem to run on fluid dynamic bearings.
To test the cooler efficiency we are going to use five consecutive runs of a pretty resource-consuming Aliens vs. Predator (2010) game with the highest image quality settings in 2560x1440 resolution with 16x anisotropic filtering and MSAA 4x antialiasing. We used MSI Afterburner 2.3.1 and GPU-Z 0.6.7 as monitoring tools. This test was performed inside a closed system case at 24°C room temperature. All thermal tests were carried out before we took the card apart, i.e. with its default thermal interface still intact.
And here are temperature data on our ASUS GeForce GTX 660 DirectCU II OC:
Auto fan mode
Maximum fan speed
In the automatic fan regulation mode, the GPU was only 62°C hot at peak load, the fans rotating at 1590 RPM only. At the maximum speed of 3540 RPM the GPU temperature was 53°C. The DirectCU II proved its highest efficiency but we wanted more. So we additionally tested it at 25% fan speed, which was 1170 RPM. The DirectCU II coped very well again, keeping the GPU as cool as 68°C.
This performance is impressive but how quiet is the DirectCU II? We measured its noise level following our traditional methodology.
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 measurements were taken outside the system case, when the only noise source was the cooling system and its fans. The noise-level meter was set on a tripod at a distance of 15 centimeters from the graphics card cooler fan rotor. The mainboard with the graphics card was placed at the edge of a desk on a foam-rubber tray. The bottom limit of our noise-level metering device 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 cards’ fans was changed with the help of a special controller supporting 0.5 V voltage adjustment increments.
Here’s the graph (the vertical dotted lines mark the top speed of the fans in the automatic regulation mode).
It is clear that the ASUS DirectCU II works quieter than the other two cards featuring original coolers. The difference is substantial. Moreover, the DirectCU II doesn’t leave the comfortable range in the automatic mode. In other words, it is not audible at all against the background noise from a quiet computer. This is in fact one of the quietest graphics cards we’ve ever tested.