We started our overclocking experiment from Samsung’s 0.4ns memory chips and found them capable of working at 4700 MHz. There were occasional image artifacts, however, so we had to roll back to 4660 MHz. The memory frequency grew by 22.6% from the default 3800 MHz, which is quite good for an Nvidia-based card with a 320-bit memory bus.
The GPU could only be stable at 810/1620 MHz (+10.7%) if we didn’t change its default voltage of 0.975 volts, so we had to increase the latter. The top stable GPU clock rate turned out to be directly proportional to GPU voltage. Unfortunately, the maximum voltage we could select was 1.1 volts, so we stopped at 930/1860 MHz. This is 27% above the default GPU clock rate. Although such a number can hardly impress the user of a 28nm Tahiti GPU, it is indeed an excellent result for Nvidia’s current 40nm chips with air cooling.
When overclocked, the ASUS got as hot as 67°C in terms of its GPU temperature, the fans rotating at 45% of their full speed (2100 RPM, 39 dBA):
The DirectCU II cooler keeps on surprising us with its highest performance. It is just designed for nothing else but overclocking.
We measured the power consumption of computer systems with different graphics cards using a multifunctional panel Zalman ZM-MFC3 which can report how much power a computer (the monitor not included) draws from a wall socket. There were two test modes: 2D (editing documents in Microsoft Word and web surfing) and 3D (the benchmark from Metro 2033: The Last Refuge at 1920x1080 with maximum settings). Here are the results:
When working at its default clock rates and voltages, the ASUS GTX 560 Ti 448 cores DirectCU II needs about as much power as the new Radeon HD 7950 and about 45 watts less than the GeForce GTX 580 3GB. But when the ASUS is overclocked, the power consumption of the respective system grows up as high as 500 watts and more. Well, this is just another proof that you need a 550W or better power supply for a computer with a graphics card of this class.