We always set the power limit to its maximum when benchmarking GeForce GTX 6xx series cards, especially in our overclocking tests. This limit is 132% with the Zotac GeForce GTX 680 AMP! Edition.
After some experimenting we managed to add 95 and 420 MHz to the card's default GPU and memory frequencies, respectively.
As a result, our Zotac GeForce GTX 680 AMP! Edition was stable at clock rates of 1206 MHz (+79 MHz in boost mode) and 7028 MHz.
That’s very good for a pre-overclocked graphics card, especially as Zotac's cooler kept the temperatures low even after our additional overclocking:
The GPU is only 69°C hot and the fans rotate at 2040 RPM.
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 2560x1440 with maximum settings). Here are the results:
Well, we already know how much power GeForce GTX 680 and Radeon HD 7970 cards need, so we don’t see anything particularly new here. Compared to the reference GTX 680, the system with the Zotac GeForce GTX 680 AMP! Edition consumes 15 watts more. When overclocked to 1206/7028 MHz, it needs an additional 14 watts. The system with the Radeon HD 7970 needs 70 watts more anyway. We can also add that a computer with any of these graphics cards would require a 550-watt PSU, which is the basic minimum for today's gaming platforms.