CREEP: Chalmers RTL-based Energy Evaluation of Pipelines

Rapport, 2017

Energy estimation at architectural level is vital since early design decisions have the greatest impact on the final implementation of an electronic system. It is, however, a particular challenge to perform energy evaluations for processors: While the software presents the processor designer with methodological problems related to, e.g., choice of benchmarks, technology scaling has made implementation properties depend strongly on, e.g., different circuit optimizations such as those used during timing closure. However tempting it is to modularize the hardware, this common method of using decoupled pipeline building blocks for energy estimation is bound to neglect implementation and integration aspects that are increasingly important. We introduce CREEP, an energy-evaluation framework for processor pipelines, which at its core has an accurate 65-nm CMOS implementation model of different configurations of a MIPS-I-like pipeline including level-1 caches. While CREEP by default uses already existing estimated post-layout data, it is also possible for an advanced user to modify the pipeline RTL code or retarget the RTL code to a different process technology. We describe the CREEP evaluation flow, the components and tools used, and demonstrate the framework by analyzing a few different processor configurations in terms of energy and performance.