Cooling System: Noise and Efficiency
The graphics card is equipped with the DirectCU II cooling system which is supposed to be 20% more efficient and 3 times quieter than the reference GTX 780 Ti cooler.
It is a large and massive thing that consists of an aluminum heatsink (with heat pipes and direct-touch technology) and a couple of fans (in a metallic casing).
The cooler has as many as five heat pipes, two of which are 6 mm in diameter. Two more pipes are 8 mm and there’s also a 10mm pipe here. The thermal grease imprint indicates that the GPU only contacts with the three central pipes.
The outermost 6mm pipes transfer heat from the sides of the adjacent pipes.
The pipes and heatsink fins are soldered to each other.
The fans are 95 mm in diameter. One of them implements the CoolTech technology, combining blower and axial fan features.
We saw the same Everflow fan in our review of the ASUS Radeon R9 290 DirectCU II.
The fans are PWM-regulated in a speed range of 1000 to 3050 RPM.
On the reverse side of the card, there is a protective plate with insulating film and perforation. It is supposed to facilitate the card’s ventilation.
The power components are cooled by a small aluminum heatsink via thermal pads.
To measure the temperature of the ASUS GeForce GTX 780 Ti DirectCU II OC we ran Aliens vs. Predator (2010) five times with maximum visual quality settings, at a resolution of 2560x1440 pixels, with 16x anisotropic filtering and with 4x MSAA.
We used MSI Afterburner 3.0.0 beta 19 and GPU-Z version 0.7.7 to monitor temperatures inside the closed computer case. The computer’s configuration is detailed in the following section of our review. All tests were performed at 25°C room temperature.
With the fans regulated automatically, the GPU is 79°C hot while the fans rotate at 1980 RPM.
This is no record for original GTX 780 Ti cards, yet a good enough result to call the cooler efficient. At the maximum speed of 3050 RPM the peak GPU temperature would drop by 9°C.
As for the power system components, their temperature was 72°C in the first test and 67°C in the second (max fan speed) test.
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.
The diagram and table below help compare the noisiness of the ASUS GeForce GTX 780 Ti DirectCU II OC with the original GTX 780 Ti cards we tested earlier: Zotac GeForce GTX 780 Ti AMP! Edition, MSI GeForce GTX 780 Ti Gaming, Inno3D iChill GeForce GTX 780 Ti HerculeZ X3 Ultra, Palit GeForce GTX 780 Ti JetStream and Gainward GeForce GTX 780 Ti Phantom. We’ve also added reference Nvidia GeForce GTX 780 Ti and AMD Radeon R9 290X cards for the sake of comparison.
The vertical dotted lines mark the top speed of the fans in the automatic regulation mode. Here are the results:
Interestingly, the noise level graph of the ASUS GeForce GTX 780 Ti DirectCU II OC almost coincides with the graph of the MSI GeForce GTX 780 Ti Gaming, but the ASUS is louder in the automatic fan regulation mode as its fans work at 1980 RPM whereas the MSI's, at 1500 RPM.
Compared to the other GTX 780 Ti versions, the ASUS is noisier than the Inno3D and Zotac but quieter than the Palit and Gainward. It is quieter than the reference coolers from Nvidia and AMD, too. Overall, the ASUS DirectCU II cooler is average in terms of noise level. Its fans didn’t rattle or anything throughout the entire speed range. In 2D mode, with the fans working at 1000 RPM or lower, the card was virtually silent.
Despite the smallest factory overclocking among all original GTX 780 Ti cards we’ve tested so far, the ASUS version has poor overclocking potential in terms of its GPU. We could only increase its clock rate by 40 MHz. Adjusting GPU voltage didn’t help because it didn’t work, actually. Enthusiasts may want to edit the card’s BIOS for that purpose, but we don’t do that in our overclocking experiments. So we have to be content with the modest +40 MHz.
On the other hand, we managed to overclock the card’s memory by as much as 1000 MHz, which is the best result we’ve seen so far. The final clock rates were 994-1060/8000 MHz.
The overclocked card had a GPU temperature of 83°C while its fans accelerated to 2120 RPM.
Since we’ve achieved such a success overclocking its memory, we’re going to see the effect the memory frequency has on the card’s performance in our tests.