Our sample of the XFX R7970 Double Dissipation Edition is a typical HD 7970 in terms of overclockability. We could increase its GPU clock rate from 925 to 1140 MHz (+23.2%) and its memory clock rate from 5500 to 7160 MHz (+30.2%).
We could not reach higher GPU frequencies while increasing the voltage from the default 1.112 to 1.300 volts even though the card could pass some tests (such as 3DMark Vantage and Unigine Heaven) at 1250 MHz and 1.24 volts. It did show visual artifacts in Aliens vs. Predator (2010), Metro 2033: The Last Refuge and some other games, so we had to roll back to the frequency we had achieved at the default GPU voltage.
When overclocked, the card grew a mere 2°C hotter in terms of GPU temperature while its fan speed increased by 130 RPM.
We guess the cooler performs excellently compared to the reference one, especially considering the huge difference in noisiness.
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 2560x1600 with maximum settings). Here are the results:
Despite the lower GPU voltage, the XFX R7970 Double Dissipation Edition needs about as much power as the reference AMD Radeon HD 7970. The difference of 4 watts is negligible and may even be due to some measurement inaccuracies. The system with two Radeon HD 7970s in CrossFireX mode consumes about 215-220 watts more than the system with one such card. Take note that the second card of the CrossFire configuration is just turned off in 2D mode, reducing the power draw to the level of the systems with only one graphics card inside. That's a handy power-saving feature implemented in the new Radeon HD 7970s.