ELECTRIC POWER MANAGEMENT UNIT, COMPUTER SYSTEM AND METHOD OF ACCESSING PLURAL CONFIGURATION REGISTERS IN ELECTRIC POWER MANAGEMENT UNIT OF COMPUTER

PURPOSE: To provide a power management unit including a plurality of component registers used to store configuration information to set various operational parameters of the power management unit. CONSTITUTION: A program register 12 is mapped in the configuration space of the computer system and used for storing an I/O address setting value of an index register 126. The program register 124 is written for initial setting of the power management unit and relates to a prescribed default. When the program register 124 is set once by an I/O address of the index register 126 and the access to the component register is attained by writing at first an offset to the index register 126. Then, configuration data are written in/read from the component register designated by executing a proper cycle to an address of the component register mapped at a location by one preceding word by the index register 126.