AccuPower: An Accurate Power Estimation Tool for Superscalar Microprocessors

Abstract

This paper describes the AccuPower toolset-a set of simulation tools accurately estimating the power dissipation within a superscalar microprocessor. AccuPower uses a true hardware level and cycle level microarchitectural simulator and energy dissipation coefficients gleaned from SPICE measurements of actual CMOS layouts of critical datapath components. Transition counts can be obtained at the level of bits within data and instruction streams, at the level of registers, or at the level of larger building blocks (such as caches, issue queue, reorder buffer function units). This allows for an accurate estimation of switching activity at any desired level of resolution. The toolsuite implements several variants of superscalar datapath designs in use today and permits the exploration of design choices at the microarchitecture level as well as the circuit level, including the use of voltage and frequency scaling. In particular the AccuPower toolsuite includes detailed implementations of currently used and proposed techniques for energy/power conservations including techniques for data encoding and compression, alternative circuit approaches, dynamic resource allocation and datapath reconfiguration. The microarchitectural simulation components of AccuPower can be used for accurate evaluation of datapath designs in a manner well beyond the scope of the widely-used Simplescalar tools.