Recently the demand on high graphic ability has increased in handheld systems due to multimedia or game application. Conventional DVS (dynamic voltage scaling) methods focus on reducing energy consumption of CPU. They didn't consider the influence of multimedia accelerators to make DVS policies. From the preliminary experiment, we found that the conventional DVS algorithm is not optimal to a system with a multimedia accelerator in context of reducing energy consumption of the system. We propose a power management mechanism that guarantees both QoS and reduction of energy consumption by considering the relation between the frequencies of the CPU and the frequencies of the multimedia accelerator. The proposed mechanism is a DVS technique in context of multimedia accelerator. We experimented the proposed mechanism on a testbed equipped with Intel XScale processor and Intel 2700 G multimedia accelerator. The experimental result shows that the proposed method reduces energy consumption of the system as much as by 33% compared to conventional CPU-only DVS algorithms.

Recently power management of display modules has become important for handheld systems. In this paper, we observe the interaction between the LCD, main consumer of the power in handheld systems, and the CPU. We propose an efficient method which reduces power consumption of the handheld system by controlling the voltage and frequency of the CPU to reduce display power. The experimental result on Mainstone II with PXA270 shows that the proposed mechanism reduces power consumption of the system by 41% and 15% for multimedia applications and web applications, respectively, when compared to the conventional DVS (Dynamic Voltage Scaling) scheme.