X-bit labs

From Extreme to Mainstream: Nvidia GeForce 8800 GT from Leadtek (page 8)

Category: Video

by Alexey Stepin , Yaroslav Lyssenko

[ 12/03/2007 | 03:09 PM ]

Cooling System

Nvidia developed a new reference cooler for the GeForce 8800 GT. It is a single-slot device with a complex internal design that should be capable of cooling the 65nm G92 chip.

We took the cooler apart to check out in interior, which was not an easy task. The casing seems plastic but is really made from metal. It is fastened to the base not only with the side locks but also with a sticker to the heatsink (probably to avoid rattling due to the vibration from the operating fan).

The photo shows three heat pipes that transfer the heat flow from the copper sole that contacts with the GPU die to the heatsink. The diagonal placement of the heatsink is logical since the cooler occupies only one slot and the hot air cannot be exhausted through slits in the mounting bracket. With the heatsink positioned like that, the hot air is thrown off the graphics card towards the interface connectors. This is no good for the temperature inside the system case, of course, yet shouldn’t be a problem for a well-ventilated case.

The cooler’s sole is made from copper while the rest of the base is aluminum. A generous amount of dark-gray thermal grease is used as a thermal interface between the GPU and the cooler. Less of it should have been quite enough for the relatively small G92 core. Perhaps a die package with a heat-spreading cap was planned originally.

There are special juts with pads soaked in white thermal grease at the spots where the cooler’s base touches the memory chips and power circuit elements. The whole arrangement is secured on the PCB with 12 spring-loaded screws. The cooler has a small radial fan that is very noisy at the max speed, which is not surprising considering its consumption current of 0.8A.

The fan uses a four-pin connection with outputs for a velocity sensor and a PWM-based speed regulation system. It works at a reduced speed most of the time – you can refer to the next section for exact numbers.

The new reference cooler from Nvidia is good overall, yet its efficiency is lower than that of the GeForce 8800 GTS due to its compact size. Despite the low heat dissipation of the new core, the system may prove unable to cool pre-overclocked GeForce 8800 GT, like the Leadtek WinFast PX8800 GT Extreme, and remain quiet. That’s why we can expect to see quite a lot of GeForce 8800 GT with a non-standard cooler.