1. A mechanism for powering down a functional unit on an integrated circuit, wherein the functional unit is clocked by its own independent clock, said mechanism comprising: means for indicating to the functional unit whether the functional unit is required for use; and means for powering down the functional unit coupled to said means for indicating, wherein said means for powering down the functional unit comprises stop clock logic in the functional unit that powers down the functional unit transparent to and independent of any other functional units on the integrated circuit when the functional unit is not required for use, wherein the independent clock of the functional unit is stopped by the functional unit when the functional unit is not in use and automatically started by the functional unit when the functional unit is required for use.