Extending Amdahl´s law for energy-efficiency

This paper presents a study about the potential dynamic energy improvement that can be achieved when hardware parallelization is used to increase the energy efficiency of the system rather than to increase performance. We show that it is possible, at early design stages, to know the number of parallel cores that allows a system to achieve the maximum energy improvement for a given throughput. Using Amdahl´s law to represent the ratio between the serial and parallel portion of an application, we can derive simple formulas to obtain the optimum frequency, supply voltage and energy improvement while the execution time remains constant.