Empirically derived abstractions in uncore power modeling for a server-class processor chip

Abstract

Early-stage power modeling is an essential aspect of the process of defining efficient, yet high-performance microarchitectures. Pre-silicon power modeling has been an active area of research and development for well over a decade, although primarily focused on the processor cores. In this paper, we examine the challenge of developing practical abstractions in uncore power modeling in an industrial setting. We report a systematic methodology of abstractions in modeling with a focus on key uncore elements of the POWER8™ processor chip from IBM. The results show that the active power of these uncore elements can be modeled with acceptable levels of precision, by: (a) using just a few activity markers: e.g. reads, writes, retries and snoops; and (b) using a small set of systematically crafted microbenchmark stress test cases to measure the activity frequencies on a detailed, cycle-and latch-accurate RTL reference model.