The present invention relates to an apparatus and method for throttling a clock of a bus used for data exchange between devices in a computer such as a portable computer or notebook. Methods according to the invention can set a throttle rate of a clock to a predetermined initial value, detect a current remaining battery capacity or a current load to the CPU, and adjust the set throttle rate to a prescribed or calculated value according to the detected remaining battery capacity or the CPU load. Thus, power consumption is reduced, and, in the case of a battery-powered computer, battery life and operating time are extended.