The first thing you notice about this card is the very unique heatsink design.
The N7800GT TOP SILENT uses the reference 7800GT PCB design, but we see an entirely different heatsink. The main heatsink itself is rather compact, with somewhat thick fins. The bundle of fins that sticks out is, however an entirely different matter.
The fins are held in place by a separate assembly that is connected to the main heatsink with a screw.
The fins themselves are connected via a heatpipe that runs through the middle of the fins. The fins are spaced very closely together.
Rotating the block of fins, as ASUS intended, worked out fine for us. A simple mechanism locks the setup firmly in place once it is fully rotated.
In this position, the block of fins would be positioned above the CPU fan in a standard setup, allowing the graphics card to take advantage of the CPU fan to cool it down as well.
We were wondering how ASUS managed to make the heatpipe movable and maintain good contact with the heatsink at the same time. It turns out that ASUS lined the ‘tunnel’ inside the heatsink with thermal paste to ensure good heat transfer. In addition, the heatpipe is also strategically located so that part of it touches the base of the heatsink, which is copper, and directly in contact with the core.