Approaching the Maximum Energy Saving on Embedded Systems with Multiple Voltages

Dynamic voltage scaling (DVS) is arguably the most effectiveenergy reduction technique. The multiple-voltage DVS systems,which can operate only at pre-determined discrete voltages, arepractical and have been well studied. However, one importantunsolved problem is how many levels and at which values shouldvoltages be implemented on a multiple-voltage DVS system toachieve the maximum energy saving. We refer this as the voltageset-up problem. In this paper, (1) we derive analytical solutionsfor dual-voltage system. (2) For the general case that does nothave analytic solutions, we develop efficient numerical methods.(3) We demonstrate how to apply the proposed algorithms onsystem design. (4) Interestingly, the experimental results suggestthat the multiple-voltage DVS system, when the voltages are setup properly, can reach DVS techniqueýs full potential in energysaving. Specifically, on the design of an ad hoc application-specificsystem and the design of the MPEG video encoder, wefind that the best single-voltage systems consume 150% and 20%more energy than the tight theoretical lower bounds, respectively.However, our approach gives dual-, 3-, and 4-voltage DVS systemsettings that are only 17.6%, 4.9%, and 2.6% for the ad hocsystem, and 4.0%, 1.1%, and 0.2% for the MPEG video encoder,over the same lower bounds.