ATI Radeon HD 4870 X2: Cooling System
Dissipating 170 watts of heat is a daunting task, considering all the restrictions concerning the design of a graphics card’s cooling system, but the Radeon HD 4870 X2 is expected to produce even more heat than its predecessor Radeon HD 3870 X2! So, we were very interested to see what cooler it came with.
Strangely enough, ATI didn’t take the problem seriously and didn’t introduce any great changes into the cooling system of the Radeon HD 4870 X2. It still consists of two solid heatsinks but, unlike on the Radeon HD 3870 X2, both are made from copper. Such heatsinks are rather effective as their ribs are a single whole with the base. As opposed to composite heatsinks, there is no additional thermal resistance where the ribs meet the sole. Still, it is rather odd that the cooler of a graphics card with a predicted power draw of 260W does not have any heat pipes (unless you count the thermal chamber on one of the heatsinks as such a pipe). There is a layer of classic dark-gray thermal grease between the GPU dies and the heatsinks.
This cooler design seems rather risky to us even if ATI achieved high efficiency by means of increasing the cooler’s fan speed (and noise). The heatsinks are fastened to the PCB with four screws and a spring-loaded back-plate. They are not connected firmly to the cooler’s frame but seem to give some heat to it anyway, which should increase the overall cooling performance a little more.
The cooler’s frame serves as a heat-spreader for the load-bearing components of the power circuit, for the memory chips located on the face side of the PCB, and for the PCI Express switch. It also serves as a seat for the fan. Elastic rubber-like pads are employed as a thermal interface. Their efficiency isn’t high, but the mentioned components do not produce as much heat as the GPUs. At the top of the frame there are a number of needle-shaped protrusions that increase its heat-spreading efficiency. The frame is fastened to the PCB with eight screws. The memory chips at the reverse side of the PCB are cooled with a separate aluminum plate.
The cooler uses the same fan as in the Radeon HD 4870’s cooler: it is the CF1275-B30H-C004 model from NTK Technologies. The peak consumption current of this fan is 1A. In other words, it can consume up to 12W at a voltage of 12V. The fan is powerful enough to cool even two heatsinks, the question is how noisy it will be while doing that.
The hot air is exhausted through the slits in the card’s mounting bracket. The card consuming some 260W, your computer may become an additional source of heat in winter. It won’t be so good in summer, though. The cooler’s casing is made from dark-brown translucent plastic. There is a sticker near the needle-shaped heatsink warning you of the high temperature of the latter.
So, the cooling system of the Radeon HD 4870 X2 is rather too simple for a graphics card with a predicted heat dissipation of 250-260W. We hope it does its job well without being a torture for your ears. We’ll check this out in the next section.