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Cooling System

The cooling system of the Toxic HD 4850 is dedicated a separate section in this review although it is not unique. As the text on the box says, the card is equipped with a Zalman VF900-Cu cooler. It is a not new but popular and universal system capable of coping with most of modern graphics cards, save for such monsters as Nvidia GeForce GTX 200 and dual-processor Radeon HD models. It deservedly received our Reader’s Choice Award in the Coolers nomination in 2007.

The translucent impeller shouldn’t mislead you: the fan lacks highlighting. The highlighted version exists and is called VF900-Cu LED.

The heatsink has Zalman’s traditional design. It is a round “flower” consisting of 160 figured copper plates. But unlike with the VF700, the plates are not pressed together to form the base of the heatsink. The heat is transferred by means of two heat pipes that pierce the heatsink plates along the perimeter and make up a closed ring. The ends of the pipes are soldered together. The cooler is fastened by means of an X-shaped plate and four threaded posts. The graphics core is protected against chipping by the metallic frame installed on it.

This cooler is highly efficient. Having a reasonable height, it allows to use not only the bottom but also the side airflow created by the classic axial fan. The base of the heat-spreader is flat and polished off to a mirror shine. Coupled with high-quality thermal grease, this ensures good thermal contact and high cooling efficiency. An additional advantage of this cooler design is that the fan also cools the PCB and memory chips. The latter are equipped with small individual heatsinks as we noted above.

The fan is connected to the header on the PCB via an adapter. It uses a classic 3-pin connection, so the PWM-based regulation pin is not utilized. There are no resistors in the +12V circuit but the official specs say that the cooler is only as loud as 25dBA even at maximum speed. It means that the Sapphire Toxic HD 4850 is going to be almost silent.

Sapphire’s choice of the cooler is good because the reference cooler of the Radeon HD 4850 is criticized for its low efficiency. It is indeed hard to expect that a compact single-slot cooler can dissipate 110 watts of heat easily. On the other hand, the Zalman VF900-Cu is a time-tested solution with high potential. The only drawback is that it blocks the neighboring slot, but this is quite normal for a modern graphics card. The performance of this cooling system will be discussed in the next section.

 
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