To overclock the AMD Radeon HD 6970 and Radeon HD 6950 cards, we used MSI’s Afterburner overclocking utility. We consider the overclock to be sufficiently stable only if the card can complete our few benchmark tests at one go.
Radeon HD 6970 overclocking
Given its default frequency of 880MHz core, it is likely that the Radeon HD 6970 was given a last-minute speed bump in order to edge out the GeForce GTX 570 in some tests. Thus, there is less headroom left for overclocking without any VGPU adjustments. With some effort, we managed to coax the Radeon HD 6970 to 950MHz core and 1450MHz (5800MHz effective) memory; that is a modest increase of 70MHz to the core and 75MHz to the memory.
Radeon HD 6950 overclocking
Using ‘defective’ silicon (die harvesting), the Radeon HD 6950 still managed a 115MHz core overclock to 915MHz, while memory overclock is similar to the HD 6970 at 1450MHz (5800MHz effective).
As the cards are voltage limited (no VGPU adjustments made), a fan speed setting of 65% on both cards was sufficient to keep temperatures below 80°C (and also to prevent us from going deaf).
If you are looking for more than just software voltage adjustment when the feature becomes available, why not take a look at our AMD Radeon HD 6970 preliminary voltage modifications article here?