X-bit labs

There Will Be Speed: The Clash of Modern Multi-GPU Technologies (page 7)

Category: Video

by Alexey Stepin , Yaroslav Lyssenko, Anton Shilov

[ 03/24/2008 | 05:01 PM ]

Cooling System

As we noted already, the GeForce 9800 GX2 differs fundamentally in its design from the ATI Radeon HD 3870 X2 as well as Nvidia’s previous-generation dual-chip solutions. A special dual-sided cooler had to be developed for it.

We didn’t take it apart completely because parts of the cooler seemed to be fastened not only with screws but also with thermal glues. We didn’t apply force to avoid damaging the card. Anyway, it is clear that the cooler uses copper soles to take heat off the GPU dies. It also incorporates flat heat pipes and a common heatsink consisting of thin aluminum plates. Dark-gray thermal grease is used as a thermal interface between the copper soles and the GPUs. There are fiber pads socked in white thermal grease between the cooler’s aluminum bottom and the memory chips. This is all traditional for Nvidia’s products.

A 5.8W Delta BFB1012L blower, familiar to us by other products from Nvidia, takes the air from both sides of the graphics card through the figured holes in the PCBs and cools the heatsink. The cooler’s casing is made from aluminum and makes the card considerably heavier.

The card’ mounting bracket is populated with DVI and HDMI ports, and there are but few slits for exhausting the hot air out of the system case. These slits are an aesthetic feature rather: they are highlighted with the bright green LEDs at work but the air flow that goes through them is rather weak. Most of the hot air is exhausted sideways as the heatsink’s ribs are placed at an angle to the mounting bracket. That’s not the best solution because this hot air will stay in the system case, worsening the thermal conditions in it: the GeForce 9800 GX2 generates quite a lot of heat in 3D mode.

More effective would be the classic positioning of DVI ports in the bottom part of the mounting bracket while the top part could be all dedicated to an exhaust hole like in the GeForce 8800 GTS 512MB or GeForce 8800 GTX. The HDMI port is not a serious advantage because its functionality is easily realized with an adapter. In SLI mode, there is only one active port and the card supports one monitor only.

The above-described cooling system developed by Nvidia for the GeForce 9800 GX2 seems to be not quite good for a card with a heat dissipation of 180-200W. A high speed of the fan is likely to be called for in order for this cooler to be effective and this will affect the card’s noise characteristics. We’ll check this out in the next section.