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Cooling System

The Radeon HD 5970’s cooling system presents some interest because the previous cooler design that AMD had developed for the Radeon HD 4870 X2 proved to be both noisy and inefficient and got quite a lot of criticism from reviewers and users. This was largely due to the layout of the cooling system with two independent heatsinks, one for each GPU. The cooler had only one fan and the air passed one GPU and then the other. As a result, the farther GPU’s heatsink received the hot air from the closer GPU and was hotter as the consequence. The use of a vapor chamber in one of the heatsinks did not help much. The GPUs of a Radeon HD 4870 X2 would quickly get as hot as 90°C and higher under 3D load. The automatic fan control system tried to cope with that by accelerating the fan from time to time, but this only made the fan unbearably loud while the changes in noise were very irritating.

We were wondering then why ATI had not designed a cooler with a common heatsink that would cool both GPUs. And now the developer has implemented this design in the Radeon HD 5970. Everything seems to be ordinary at first sight:

We can see standard copper soles of heat-exchangers and typical dark-gray thermal grease where the heat-exchangers contact with the GPU dies. There are thermal pads ensuring contact with the memory chips, PCI Express chip and the voltage regulator’s elements. But as soon as we remove the plastic casing, the difference of the new layout from the old one becomes apparent:

Instead of two heatsinks there is only one now. It is larger and has no heat pipes. This does not look efficient but the heatsink is connected to a massive vapor chamber that contacts with both GPUs, distributes the heat uniformly and transfers it to the heatsink consisting of thin aluminum plates.

ATI claims this vapor chamber can dissipate 400 watts of heat, which is far higher than the peak heat dissipation of the Radeon HD 5970. The vapor chamber is pressed into the aluminum base that has contact with the other components that require cooling. The needle-shaped ribbing in the top part of the base improves its efficiency as an auxiliary heatsink.

The cooling system is equipped with an NTK (HK) Limited FD9238H12S fan. The same fan is used in the Radeon HD 5870 and 5850 coolers. Judging by the marking, the fan has an output power of 9.6 watts (0.8A/12V) which means a high level of noise at maximum speed. This cooler with a common vapor chamber for both GPUs and a heatsink with large dissipation area should cool the card effectively at comfortable noise. We are going to check this out in practice in the next section.

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