To overclock the AMD Radeon HD 7950 video card we used AMD Overdrive to find the highest stable overclock without any voltage increases.
The AMD Radeon HD 7950 video cards come clocked at 800MHz on the core and 1250MHz on the memory. If you use CATALYST Control Center (CCC) like we are 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 1100MHz on the core and 1575MHz on the memory. We were able to run each card at 1000MHz on the core and 1575MHz on the memory. If we went up to 1005MHz on the core of each card it would lock up during gaming and 3DMark11 benchmarking. With the core set to 1GHz (1000MHz) it was rock solid and we played BF3 for several days crash free with these settings.
Here is a GPU-Z screenshot showing CrossFire enabled and the cards running at 1000MHz on the core and 1575MHz on the memory! This is a 200MHz overclock on the core and 325MHz on the 3GB of GDDR5 memory.
Radeon HD 7950 CrossFire at 800MHz core and 1250MHz memory:
Radeon HD 7950 CrossFire at 1000MHz core and 1575MHz memory:
We tried out this overclock with Futuremark 3DMark 11 on the performance preset and saw the score go from P12579 to P14560, which is a 15.7% or 1981 3DMark point increase from the cards stock settings. Not bad performance and we are sure that these cards have more in them if you wanted to increase the GPU Voltage, but we did not want to get into that today. We just wanted to show you that what the cards could do with basic overclocking methods and hitting 1GHz on both cards in CrossFire was nice to see!