A DVS system based on the trade-off between energy savings and execution time

DVS (dynamic voltage scaling) is a technique used for reducing the power consumption of digital circuits. The power consumed by these circuits has a main component (dynamic power) that is proportional to the square of the supply voltage. Additionally, for every supply voltage, there is a maximum value of the clock frequency. The advantage of using DVS is that the supply voltage (and hence clock frequency) can be adjusted depending on the specific needs during execution. The DVS concept has been used in some commercial products like Transmetapsilas Crusoe, Intel Speed Step, AMD K6, Hitachi SH4, etc. This paper presents results obtained by using a DVS algorithm based on the workload estimation and trade-off between the execution time and power savings. It is discussed about influence of the power supply´s slew rate, algorithms influence on the system performance and problems to estimate the processors workload. The DVS system is realized on Intel´s PXA255 platform and energy savings have been calculated by measuring directly voltages and currents on the platform.