Accurate Characterization of the Variability in Power Consumption in Modern Mobile Processors.

The variability in performance and power consumption is slated to grow further with continued scaling of process technologies. While this variability has been studied and modeled before, there is lack of empirical data on its extent, as well as the factors affecting it, especially for modern general purpose microprocessors. Using detailed power measurements we show that the part to part variability for modern processors utilizing the Nehalem microarchitecture is indeed significant. We chose six Core i5-540M laptop processors marketed in the same frequency bins - thus presumed to be identical - and characterized their power consumption for a variety of representative single-threaded and multithreaded application workloads. Our data shows processor power variation ranging from 7%-17% across different applications and configuration options such as Hyper-Threading and Turbo Boost. We present our hypotheses on the underlying causes of this observed power variation and discuss its potential implications.