Dynamic Power Management Methodologies using Hardware Model-based Simulator

Wireless Networks Subgroup: Embedded Systems The increasing need for high performing portable systems has brought about an interest for techniques related to energy consumption reduction. One promising technique is Dynamic Voltage Scaling (DVS), where the key idea is to adjust the performance (voltage supply and clock frequency) of the processor according to the processor load. For this purpose a number of general-purpose and DSP processors are introduced, with the capability of making on the fly adjustments of the processor supply voltage and clock frequency. The object of this project is to gain knowledge within the area of DVS methods. This is achieved by an extensive survey of the DVS literature. In order to evaluate the DVS methods we have designed and implemented a simulator based on an execution model. As input the simulator uses a task-set specification and this task-set is then executed on the execution model containing models of a RTOS and the hardware. The purpose of the simulator is to investigate the effect of the DVS like voltage/frequency transition overhead, energy gain, etc. The hardware model used is based on the Analog Devices Blackfin DSP processor, specific the BF535 EZ-KIT Lite evaluation board. The result of our work show that the task-set specification is of great influence on the amount of energy saving that is obtainable. Typical the voltage/frequency transition overhead is of reasonable size, resulting in the possibility of energy increase when task periods are of same duration as the transition overhead. We also see that the DVS methods perform very differently according to the task-set specification; specifically the utilization and worst to best case ratio have impact on the performance. The conclusion is, that it is very beneficial having estimates of the energy consumption and having the the possibility of evaluating DVS methods performance for the specific task-set. The project is a one year CISS project initiated in January 2003 in cooperation with Analog Devices Aalborg, att. Finn Büttner. (Anders Brødløs Olsen and Peter Koch)