Cooling System Design

It is the cooling system that presents the biggest interest in the Palit Revolution 700 Deluxe. As we have written above, the reference cooler from ATI is deservedly criticized for mediocre performance coupled with much noise. Developing such a cooler is not easy because 130 watts of heat must be taken off each graphics core of the Radeon HD 4870 X2, besides such other components as memory, power transistors of the voltage regulators, etc. Let’s see how Palit has solved the problem and got rid of the abovementioned downsides.

Even before we removed the cooler’s casing it was clear that the manufacturer had gone the easiest way. The developer had used a three-slot cooler design in order to increase the height of the heatsinks and their heat dissipation area.

As you see, each of the two graphics processors of the Revolution 700 Deluxe is cooled with an individual heatsink consisting of thin aluminum plates.

Each heatsink has a copper base connected with two heat pipes to the ribs and is fastened to the PCB with four screws and an X-shaped back-plate that ensure proper thermal contact with the GPU die. The thermal interface seems to be ordinary gray thermal grease, but it is actually some thermoplastic material that is dry when cold. At least we had to scrape it off carefully before applying a layer of fresh thermal grease when we assembled our Revolution 700 Deluxe.

The other hot components on the face side of the PCB, such as memory chips, are cooled with a large aluminum plate with additional heatsinks. Two kinds of thermal interfaces are used here: green elastic pads for the memory chips and PCI Express switch and dark-gray grease for the power transistors of the voltage regulators.

Another such plate is installed on the reverse side of the PCB and fastened to the first plate with screws. It cools the memory chips located there.

Two 9-blade 80mm fans from Power Logic (PLA08015B12HH, 4.2W, 12V, 0.35A) are installed on the cooler’s casing. They are connected in parallel and have PWM-based speed control.

This cooler seems to have high potential and should cope with a Radeon HD 4870 X2 without much noise, but it has one serious downside. It does not exhaust the hot air out of the system case. The heatsink ribs are positioned in parallel to the mounting bracket and the airflows from the heatsinks are oriented likewise. Thus, most of the hot air remains within the computer – and the total heat dissipation of two RV770 chips is as high as 250W! This graphics card really needs a well-ventilated system case. Otherwise, not only the graphics card but also other system components may overheat.

Before we proceed to the gaming tests, we will see how effective Palit’s original cooler is and how it affects the overclocking potential of the Revolution 700 Deluxe.