Board analysis

Top of the ASUS Extreme X1800 XT TOP

Back of the card

At first glance the ASUS board looks much larger than stock X1800 XT

At first glance, ASUS’ Extreme X1800 XT TOP looks like no other Radeon X1800 XT card on the market. Sitting next to ATI’s own Radeon X1800 XT reference board, the ASUS Extreme X1800 XT TOP looks massive. It even looks large sitting next to a GeForce 7800 GTX 512MB. But actually, the board is based entirely on ATI’s reference board design for the Radeon X1800 XT. ASUS makes no changes to the board’s PCB – the dimensions of the PCB are the same and the card’s core components are indistinguishable. The sole difference lies in the Extreme X1800 XT TOP’s unique cooling.

...and the 7800 GTX 512MB

Back plate of ASUS X1800 XT TOP and reference X1800 XT from ATI

The board’s most notable feature is without a doubt its dual-slot cooling. Like their Extreme N7800 GTX TOP we reviewed earlier this year, ASUS uses a cooling solution from Arctic Cooling on their Extreme X1800 XT TOP. In this case though, the cooler is unique to ASUS, according to Arctic Cooling, they have no plans at this time to release the cooler to the public.

The cooler is very large and is composed of multiple pieces. At the heart of the cooler are four heatpipes, which are responsible for keeping the graphics core cool. Heat pipes work by transferring heat through a continuous condensation – evaporation cycle. Each of the heat pipes is filled with distilled water. As the graphics core heats up, the distilled water in the heat pipe begins to boil, forcing hot vapor to the other end of the heat pipe where it is cooled. Here the vapor condenses back to the liquid phase and returns to the other end of the heat pipe. This condensation – evaporation cycle is continually in motion, working to keep the graphics core cool.

This cycle generates a lot of heat. As anyone who’s owned a Zalman VGA heat pipe can tell you. Therefore, to help keep the graphics core and heat pipes cool, Arctic Cooling uses a large copper base, which rests just above the R520 GPU, enveloping the heat pipes.

Finally, cooling all of this is a large aluminum heatsink with thin, long fins. This is where the bulk of the cooling’s size comes from, as the fins are just shy of 1.5” long. By integrating lots of thin, long fins, the heatsink’s surface area is increased, thus improving its effectiveness as heat is drawn up the fins. The downside is that as a result, the card will eat up the slot directly adjacent to your graphics slot.

Massive cooling

Mockup of the Arctic Cooling unit

Like the VGA Silencer line, the fan Arctic Cooling uses is large in diameter, allowing them to spin the fan at lower RPMs while still generating a considerable amount of airflow. Since it spins at lower RPMs, the fan generates less noise: although we wouldn’t say it runs silent, but it’s definitely an improvement over the stock cooler ATI and their board partners use on their Radeon X1800 XT cards.

Larger heatsink on the ASUS card (top)

ASUS also places a large black aluminum heatsink on the Extreme X1800 XT TOP’s power circuitry located just behind the card’s cooler. On stock X1800 XT cards, a thin red aluminum heatsink is used. With the Extreme X1800 XT TOP running at higher clocks (and thus requiring more power) ASUS must have felt that the stock cooling wasn’t sufficient, replacing it with a larger, more robust heatsink.