AMD Radeon HD 6970 & HD 6950 Review - PAGE 4

The new cooling solution used on the HD 6900 series does away with the standard heatpipe design used on the Cypress architecture in favor of a large vapor chamber heatsink. This is AMD's 5th generation of vapor chamber cooling, with the first edition dating back to the days of the HD2900. Of course in that time AMD has refined the design of the heatsink to its current form. The heasink now consists of a massive copper base that makes direct contact with the GPU to ensure the heat is transferred through the vapor chamber and into the aluminum finned array in the most efficient manner.

This design transfers heat more evenly through the array, so the air moving through the cooler is better able to exhaust the heat. This effectively reduces the needed air flow, so the overall acoustics level is decreased as well. NVIDIA implemented a similar vapor chamber design on their newly released 500 series graphics cards, so both companies are now utilizing similar cooling on their high-end products.

The back plate easily comes off and reveals a very clean layout for Cayman-based graphics cards.

The heatsink shroud is attached by eight locking clips that run along the sides. With the cover removed, you can see that the fan sits about a half-inch behind the heatsink, allowing the air from the fan to more evenly enter into the finned array. Additionally, the fan uses a 4-pin PWM connector that allows the graphics card to adjust the RPM level in real-time.

To ensure the heat is able to transfer to the cooler, AMD pre-applies a thermal compound to the base of the vapor chamber. There are also eight thermal pads aligned on the black heatspreader that transfer heat away from the memory chips. Unfortunately, this is the best view of the base that we could get because the vapor chamber heatsink is actually glued to the base of the heat spreader.

The HD 6970 and HD 6950 look identical down at the PCB level, with the only exception being the on-board power connectors.The overall layout of the boards is very similar to those used by Cypress-based graphics cards and AMD has even relocated the VRM back to the end of the PCB. When AMD released the Barts architecture, the VRM was moved to the front of the PCB, which in theory improves the cooling of the graphics card by eliminating the hot air generated by the VRM from being blown over the GPU.

Overclocking:

Overclocking the HD 6970 and HD 6950 was done via MSI's Afterburner overclocking utility. The HD 6970 comes with a default GPU clock of 880MHz, which is already high, so I wasn't expecting to there to be to much additional headroom. As far as the GPU clock speed I was dead on, and I was only able to adjust the total speed by 82MHz, which set the final clock at 962MHz. As for the memory though, it had plenty of headroom for overclocking and I was amazed that it was able to achieve a stable memory rating of 1549MHz (6.2Gbps QDR)!

The HD 6950 has a slightly slower default clock speed, which helped increase overclocking potential. We were able to increase the GPU frequency by 108MHz, thus giving the GPU a 908MHz clock speed. Like the HD 6970, the memory was able to overclock quite substantially, and would only start to artifact after 1451MHz (5804Gbps QDR).

While overclocking the graphics cards it was essential to maintain a temperature rating below 86°C. To do this I increased the fans RPM level, which greatly reduced the core temperature, but at the cost of a higher acoustic level.