Overclocking with ASUS GPU Tweak
ASUS GPU Tweak has a very large overclocking range. The stock settings allow the GPU Boost Clock on the ASUS GTX 660 Ti DC II TOP to increase to 1359MHz and the memory frequency to increase to 8008MHz. While we did not get that high of an overclock, we still enabled Overclocking Range Enhancement to fully unlock the program. To do this, click settings and select the Tuning tab. Inside of this tab, select the Tune Setting tab, and check the box for Overclocking Range Enhancement. This allows users to increase the GPU Boost Clock to 2274MHz and the memory clock to 9999MHz.
Our first step in overclocking the ASUS GTX 660 Ti DC II TOP is to increase Power Target to its highest level. As we said earlier, the new BIOS allows us to increase it to 123%, while the stock BIOS allows Power Target up to 114%. We also set the fans to the highest level, 100%, to keep off any extra heat that is generated as a result of higher clock speeds. The DirectCU II cooling system was surpr***ngly quiet with fans at 100%.
ASUS GPU Tweak also lets users increase the minimum GPU voltage. The highest amount available for the ASUS GTX 660 Ti DC II TOP is 1.175 volts. This basically forces the ASUS GTX 660 Ti DC II TOP to run at 1.175 volts, compared to the voltage during normal testing which only increased to 1.62 volts. The next step is to find the highest stable GPU Boost clock. We increased the GPU Boost clock from by 88MHz up to 1225MHz. Any value higher than this would cause crashes or severe artifacts. We did not experience a very high overclock on the memory. The memory frequency increased by 103MHz, from 1502MHz (6GHz GDDR5) up to 1605MHz (6.42GHz GDDR5).
The GPU Frequency is the base clock speed that we will see while playing a video game. The GPU Clock speed is the frequency the video card will not go under in game. The GPU Boost Frequency is what the GPU clock is guaranteed to go up to in most games. Basically, the higher we get this number, the higher operating frequency we will get. Although GPU-Z may report one number for GPU Boost, the actual operating frequency in game is higher than this. We will be referring to this number as "Top GPU Boost" or "actual frequency."
A reference GeForce GTX 660 Ti has a GPU frequency of 915MHz and a GPU Boost frequency of 980MHz. The memory on a reference GeForce GTX 660 Ti is 1502MHz (6GHz GDDR5). The factory overclock on the ASUS GTX 660 Ti DC II TOP increases the reference GPU frequency by 144MHz up to 1059MHz. The GPU Boost frequency has an increase of 157MHz up to 1137MHz. These result in a Top GPU Boost or actual frequency in game of 1293MHz. The memory runs at the stock speed of 1502MHz (6GHz GDDR5).
After manually overclocking the ASUS GTX 660 Ti DC II TOP the GPU frequency was 1147MHz. This is 88MHz faster than the out-of-box video card and an overall increase of 232MHz compared to a reference video card. The GPU Boost frequency peaked at 1225MHz, 88MHz faster than the stock video card and 245MHz faster than the reference model. This resulted in a Top GPU Boost or actual frequency in game of 1382MHz. This is the actual frequency we got in games and is the most important number to keep in mind. The memory ran 103MHz faster than a reference video card at 1605MHz (6.42GHz GDDR5).
Below is a screenshot of GPU-Z after achieving our highest stable overclock on the ASUS GeForce GTX 660 Ti DirectCU II TOP video card. We will be using this operating frequency as a fourth video card in this evaluation.