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Cooling System: Efficiency and Noise

We’ve already seen this cooler with four 6mm copper heat pipes and a copper base in our review of the Zotac GeForce GTX 670 AMP! Edition.

We were not sure whether the pipes and copper base were soldered to each other, but they seem to be, judging by the dots that become visible where the base gets hot.

The two fans are attached right to the heatsink and covered with a metallic casing from above.

The heat pipes pierce the right part of the heatsink. The fins are soldered to the base, which is the only way for the heat to get to the left part of the heatsink.

The fins, soldered to the pipes too, are 0.3 millimeters thick and 2 millimeters apart from each other. There are small aluminum heatsinks with thermal pads mounted on the power components and memory chips.

Two 7-blade 92x12mm fans are set to blow at the heatsink.

Labeled MGT9212YB-W20, they are manufactured by Protechnic Electric.

Judging by the sticker, the peak power draw of each fan is 5.8 watts at 0.48 amperes. The speed is PWM-regulated from 1350 to 3600 RPM but the top speed is actually limited to 85% in the graphics card’s BIOS.

We checked out the card’s temperature while running Aliens vs. Predator (2010) in five cycles at the highest settings (2560x1440, with 16x anisotropic filtering and 4x antialiasing).

We used MSI Afterburner 2.2.2 and GPU-Z 0.6.2 as monitoring tools. This test was carried out with a closed system case at an ambient temperature of 25°C. We didn’t change the card’s default thermal interface. Let's see how efficient Zotac's exclusive cooler is on the top-end GTX 680:


Auto fan mode

Maximum fan speed

With the fans regulated automatically, the GPU temperature was as high as 78°C, the fans rotating at 2220 RPM (or 46% of their full speed). And if the speed is manually set at 3600 RPM (85%, which is the maximum set in the graphics card's BIOS), the GPU is 7°C cooler and has a temperature of 71°C at peak load. Considering that this is a pre-overclocked card whose GPU can occasionally work at 1189 MHz, the results are satisfactory, although the same cooler had done much better on our Zotac GeForce GTX 670 AMP! Edition.

We had some doubts about these results, though, so we replaced the default thermal interface with Arctic MX-4. We were astonished at the difference:


Auto fan mode

Maximum fan speed

The GPU temperature lowered by as much as 13°C in the automatic regulation mode, so the GPU was only 65°C hot and the fans slowed down from 2220 to 1950 RPM. At the maximum 3600 RPM, the temperature was 59°C or 12°C lower than with the default thermal interface. Well, we don’t want to blame the thermal interface alone. Perhaps the factory assembly of the cooler wasn’t perfect (one of the screws wasn’t tightened up, although the thermal grease imprint on the GPU seemed to be okay). Anyway, the fact is that we significantly increased the efficiency of Zotac's cooler by replacing the default thermal interface.

Then 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 reference Nvidia GeForce GTX 680 and the ASUS GeForce GTX 680 DirectCU II TOP into the next diagram for the sake of comparison (the ASUS card has a highly efficient and quiet cooler). Here are the results (the vertical dotted lines indicate the top speed of the fans in automatic regulation mode):

Unfortunately, the Zotac GeForce GTX 680 AMP! Edition isn't quiet. Yes, the original cooler from Zotac is quieter than the reference GeForce GTX 680 in the automatic fan regulation mode, but it is much worse than the one installed on the ASUS GeForce GTX 680 DirectCU II TOP, which seems to be the best cooler among all serially manufactured graphics cards.

We’d recommend Zotac not only to change their fan supplier because the fans rattle at low speed but also limit the bottom speed to 1000 rather than 1350 RPM. This would make the card quieter and even silent in 2D applications.

 
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