The heatsink used on the Ultimate Edition HD 4670 is a passive design. This means that its sole means of discharging the thermal load, is to rely on the temperature differential between the air in the chassis and the heatsink itself. Of course better case airflow will allow the heatsink to be more effective. Sapphire has come up with creative solutions for cooling ATI based video cards over the past year with the Toxic and Atomic series of video cards. Vapor Chamber cooling and water cooling are two of the avenues they have explored successfully. But now on the Ultimate Edition, the silent heatsink uses two heatpipes attached to a copper plate to and aluminum block and fin array. As large as the heatsink is, it should prove to be effective at cooling this series of cards.