a system for automatically adapting the power conservation functions of a personal computer to the work patterns of any user . a power control system of the pc monitors activity of i / o devices and if upon the elapse of a first time interval a particular i / o device or combination of devices has not been accessed , one or more i / o devices are powered - down . following power - down , the first time interval is incrementally increased if i / o activity immediately occurs thereafter , prior to elapse of a second time interval . this process may repeat itself several times until the first time interval reaches a maximum value . alternatively , if , following power - down , i / o activity does not occur until after elapse of a third time interval , the first time interval is incrementally decreased until the first time interval reaches a minimum value . the system thereby automatically adapts to maximize power conservation during periods of low activity while preventing user disruption during periods of increased activity .