To overclock the AMD Radeon HD 7000 series cards we usually use AMD OverDrive:
The Sapphire HD 7950 OC Edition is already factory overclocked and comes clocked at 900MHz on the core and 1250MHz on the memory from the start. The reference AMD Radeon HD 7950 that AMD sent us was clocked at 800MHz core and 1250MHz memory. By using 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 1100MHz on the core and 1575MHz on the memory. We know this card can do well over those limits, so we will not be using Catalyst Control Center or OverDrive for overclocking.
Instead, we will be using the latest version of SAPPHIRE’s TriXX overclocking utility (v4.1.0). TriXX allows tuning of GPU voltage as well as core and memory clocks, whilst continuously displaying temperature. Manual control of fan speed is supported, as well as user created fan profiles and the ability to save up to four different performance settings.
The TriXX utility allows for much higher clock speed adjustment and it has GPU voltage adjustment, so we should be able to really push this card.
We left the voltage alone and found that we were able to reach 1065MHz on the core and 1600MHz on the memory with full stability. If we went up to 1070MHz on the core we would see artifacts in the benchmark, so without increasing the core voltage this is the best that we could manage. This is an increase of 165MHz on the core clock with no voltage adjustments and just a few minutes of work.
With the voltage increased from 1090mV to 1237mV we were able to hit 1185MHz on the core and 1600MHz on the memory with full stability. In all honesty we didn’t try to get the memory up any higher as we were more focused on seeing what the core clock could do. This is the highest that we could get the card with 100% stability for 24/7 use.
With a little more voltage we could run a few benchmarks at 1200MHz, but it wasn’t fully stable no matter what voltage we set for the card. Being able to just run a benchmark at 1.2GHz on a Radeon HD 7950 was fun, so we will have to call overclocking a huge success with this card.
Let’s take a look at some Futuremark 3DMark11 on the performance preset to see how the overclock helped performance.
SAPPHIRE HD 7950 OC Edition at 900MHz core and 1250MHz memory:
SAPPHIRE HD 7950 OC Edition at 1065MHz core and 1250MHz memory:
SAPPHIRE HD 7950 OC Edition at 1185MHz core and 1250MHz memory:
We tried out this overclock with Futuremark 3DMark 11 on the performance preset and saw the score go from P7597 to P9522, which is a 25.3% improvements from the cards factory overclocked settings. The reference AMD Radeon HD 7950 scores P6926, so this is a 37.5% improvement over the reference card! The SAPPHIRE HD 7950 OC Edition is an amazing overclocker and the Dual-X GPU cooler does an excellent job at keeping the card cool and quiet when overclocked at 1200MHz!