Instruction level power profiling

Abstract

This paper describes a method to model the software component of energy dissipation from an architectural description of an embedded system. An embedded system is characterized by a dedicated processor (a DSP processor or an "off the shelf" microprocessor) and the application specific software that runs on it. The hardware model of the system consists of several interacting modules (e.g. ALU, register file, controller etc.). A black box model of a cell from each module is built which consists of a table of switching capacitances (from IRSIM-CAP) for each combination of previous to present input transitions. Using this black box cell model and the past and present inputs to the module it is possible to accurately calculate the energy dissipation of the module. By performing a simple "bookkeeping" operation of all the modules activated during the instruction, it is possible to exactly estimate the energy dissipation of an instruction. A power profiler (PPROF) is built which takes as an input the program and the model of the basic units of each module and profiles the energy for each instruction of the program. In addition, it also outputs the energy consumption statistics for each type of instruction and for each module. A programmable microprocessor with sixteen instructions has been designed, and programs written for this machine are analysed using PPROF. The results of the estimated instruction energy are within 8% maximum error when compared with IRSIM-CAP.