Architectural and compiler support for energy reduction in the memory hierarchy of high performance microprocessors

In this paper we propose a technique that uses an additional mini cache located between the I-Cache and the CPU core, and buffers instructions that are nested within loops and are continuously otherwise fetched from the I-Cache. This mechanism is combined with code modifications, through the compiler, that greatly simplify the required hardware, eliminate unnecessary instruction-fetching, and consequently-reduce signal switching activity and the dissipated energy. We show that the additional cache, dubbed L-Cache, is much smaller and simpler than the I-Cache when the compiler assumes the role of allocating instructions in it. Through simulation, we show that, for the SPECfp95 benchmarks, the I-Cache remains disabled most of the time, and the "cheaper" extra cache is used instead. We present experimental results that validate the effectiveness of this technique, and present the energy gains for most of the SPEC95 benchmarks.