A microelectronic device according to the present invention is made up of two or more functional units, which are all disposed on a single chip, or die. The present invention works on the strategy that all of the functional units on the die are not, and do not need to be operational at a given time in the execution of a computer program that is controlling the microelectronic device. The present invention on a very rapid basis (typically a half clock cycle), therefore, turns on and off the functional units of the microelectronic device in accordance with the requirements of the program being executed. This power down can be achieved by one of three techniques; turning off clock inputs to the functional units interrupting the supply of power to the functional units, or deactivating input signals to the functional units. The operation of the present invention results in a very significant reduction in power consumption and corresponding heat dissipation by the microelectronic device as compared to the conventional approach of keeping all functional units operational all of the time.