We have overclocked more than a dozen AMD Radeon HD 7970 video cards over the past six months, so we have a pretty good feel for how to overclock them and how they should perform.
The AMD Radeon HD 7970 GHz Edition comes clocked at 1050MHz on the core and 150MHz on the memory from the start. The original reference AMD Radeon HD 7970 that AMD sent us was clocked at 925MHz core and 1375MHz memory, so this card is already overclocked by 13.5% on the core and 9% on the memory thanks to the 125MHz clock boost on both. By using OverDrive in CATALYST Control Center (CCC) you can raise or lower the clock frequencies within the parameters set by AMD. For this card AMD set limits for this particular BIOS to 1500MHz on the core and 2000MHz on the memory.
We used CCC and found that with the power control settings maxed out at 20 we could
hit 1205MHz on the core and 1625MHz on the memory before any artifacts
started to show up in our benchmarks. This is a great overclock as it is 155MHz over the default clock speed of 1050MHz.
We tried to push this overclock further with the Sapphire TriXX overclocking utility since it has a way to adjust the GPU voltage. Once we opened TriXX we discovered that AMD was already running the card at 1256mV, which is higher than what a standard card used to run at. We tried turning up the GPU voltage to 1325mV and 1350mV could not get any higher GPU clock stable.
Our top overclock was 1205MHz on the core and 1625MHz (6500MHz effective) on the GDDR5 memory. Our highest stable overclock ever on a Radeon HD 7970 was 1310MHz on the core clock of the Sapphire HD 7970 OC. Not a bad overclock and we were able to break the 1.2GHz barrier with no manual voltage adjustment with the stock GPU cooler!
Let’s take a look at some Futuremark 3DMark11 on the performance preset to see how the overclock helped performance.
AMD Radeon HD 7970 GHz Edition at 1050MHz core and 1500MHz memory:
AMD Radeon HD 7970 GHz Edition at 1205MHz core and 1625MHz memory:
We tried out this overclock with Futuremark 3DMark 11 on the performance preset and saw the score go from P9200 to P10068, which is a 9.4% improvements from the cards factory overclocked settings.