The Asus SilentCool heatsink is actually a dual slot cooling solution, (the silver Asus emblem extends down past the first expansion slot), although it doesn't look like one at first glance. Since the heatsink is passively cooled, it wouldn't be advisable to fit something in just below the card anyhow.

It's comprised of one large extruded aluminum heatsink which comes in contact with GPU core (via a thin copper pad), surrounds an 8mm diameter heatpipe, and extends out towards the videocard memory DRAMs. The SilentCool heatsink is held fast via a plastic mounting plate on the back of the card.

There is nothing on the back of the videocard that requires cooling.

This is all pretty standard stuff, except for the heatpipe, and what it does. The nickel-plated heatpipe is bent at 90 degrees, with a portion nested in the body of the heatsink over the GPU, and a portion extending out to a big stack of nickel-plated copper cooling fins. The entire heatpipe cooling assembly rotates 90 degrees, or when installed in a computer from a horizontal to vertical orientation. An external steel frame gives it added support, and clicks into position at either extreme.

	experts tip: radiator orientation
	the rotating portion of the en7800gt top silent/2dhtv/256m heatsink can be oriented in one of two positions, parallel or perpendicular to the videocard pcb. when the videocard is used by itself or in the top slot in a sli setup, the radiator is to be set to be perpendicular to the videocard pcb. this way the silentcool radiator can take advantage of the fan suction from the cpu cooler to draw cool air over its fins. the radiator should only be run in a parallel position to the pcb when it is being used as a secondary card in the bottom slot, say for an sli set up. in this case there is not enough space for the radiator to be placed in a perpendicular position.
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This arrangement permits the heatpipe's cooling fins to be situated over the CPU fan air intake, or another spot where it can best take advantage of system airflow. The workmanship of the Asus SilentCool heatsink is top notch on the whole. Some of the fins may have sharp edges, so be a little cautious when handling the videocard though.

As the heat travels, the GPU makes contact with a copper heatspreader which transfers the heat energy into the heatpipe. The heatpipe moves the heat energy away from the core towards the assembly of 52 fins. The SilentCool cooling solution found on the Asus EN7800GT TOP Silent/2DHTV/256M is designed to work with system airflow alone, so the computer will have to utilize case fans at the very least. When the radiator is perpendicular to the videocard, it is designed to work with the CPU fan, sucking air through the fins SilentCool radiator fins first before the air is used to cool the processor.

Testing A Silent VGA Heatsink's Effectiveness