Asus' support page is listing an entry in their frequently asked questions on the usage of ATI's dynamic overclocking feature called OverDrive. This functionality was first introduced with Catalyst 3.8 and is relying on implemented temperature monitoring. Asus 9800XT graphic cards do not follow the ATI reference board design and use a Winbond thermal sensor that is not supported by the ATI Catalyst drivers. Asus is currently looking into the possibility to release a modified driver but suggests that using their Smart Doctor tool is the only and better option to overclock your card.