An integrated processor is provided that includes a CPU core coupled to a variety of on-chip peripheral devices such as a DMA controller, an interrupt controller, and a timer. The integrated processor further includes a power management message unit coupled to the DMA controller, interrupt controller, and timer for monitoring the internal interrupt and bus request signals of the integrated processor. The power management message unit may also monitor other selected activities of the integrated processor such as activities of a floating-point coprocessing subunit. Based on the detected activities, if any, the power management message unit encodes a message on a power management message bus to thereby provide information regarding the internal events of the integrated processor to an external power management unit. Power management decisions are made by an external power management unit. The power management unit receives the encoded messages on the power management message bus and responsively makes decisions as to the appropriate power management mode to enter. The power management unit includes a clock control unit coupled to an internal clock generator of the integrated processor for controlling the frequencies of a CPU clock signal and a system clock signal. The power management unit further includes a power control unit for controlling the application of power to various external peripheral devices.