Abstract: An apparatus and method for controlling interrupts in a computer are disclosed, in which programmable software operates to control when data concerning the interrupt having highest priority is to be provided, and hardware logic operates to control how that data is provided. An interrupt vector register is included in the computer CPU. The interrupt vector register does not act like the typical register. It is not a physical register, and cannot be written to. A read to this register by the programmable software, triggers the hardware logic. Once triggered, this logic performs certain control tasks, the end result of which is returning to the programmable software, a vector corresponding to the interrupt having highest priority. The programmable software can implement various software policies, in addition to the hardware policy implemented by the hardware logic.

Abstract: A method and apparatus for operating an integrated in a reduced-power consumption state are described. The apparatus comprises power-reduction logic which, to place the integrated circuit in the reduced-power consumption state, gates a clock signal to both first and second sets of functional units within the integrated circuit. The first set of functional units is distinguished in that it is required to perform cache coherency operations within integrated circuit. The apparatus includes an input which is coupled to receive a signal indicating a memory access, to a memory resource accessible by the integrated circuit, by a further device external to the integrated circuit. In response to the assertion of this signal, the power-reduction logic propagates the clock signal to the first set of functional units, to enable this set of functional units to perform a cache coherency operation which may be necessitated by the memory access by the external device.