XTREM: A power simulator for the intel XScale® core

Managing power concerns in microprocessors has become a pressing research problem across the domains of computer architecture, CAD, and compilers. As a result, several parameterized cycle-level power simulators have been introduced. While these simulators can be quite useful for microarchitectural studies, their generality limits how accurate they can be for any one chip family. Furthermore, their hardware focus means that they do not explicitly enable studying the interaction of different software layers, such as Java applications and their underlying Runtime system software. This paper describes and evaluates XTREM, a power simulation tool tailored for the Intel XScale microarchitecture. In building XTREM, our goals were to develop a microarchitecture simulator that, while still offering size parameterizations for cache. TLB, etc., more accurately reflected a realistic processor pipeline. We present a detailed set of validations based on multimeter power measurements and hardware performance counter sampling. Based on these validations across a wide range of stressmarks, Java bench-marks, and non-Java benchmarks. XTREM has an average performance error of only 6.5% and an even smaller average power error: 4%. The paper goes on to present a selection of application studies enabled by the simulator. For example, presenting power behavior vs. time for selected embedded C and Java CLDC benchmarks, we can make power distinctions between the two programming domains as well as distinguishing Java application (JITted code) power from Java Runtime system power. We also study how the Intel XScale core's power consumption varies for different data activity factors, creating power swings as large as 50mW for a 200Mhz core. We are planning to release XTREM for wider use, and feel that it offers a useful step forward for compiler and embedded software designers.