An efficient direct mapped instruction cache for application-specific embedded systems

Caches may consume half of a microprocessor´s total power and cache misses incur accessing off-chip memory, which is both time consuming and energy costly. Therefore, minimizing cache power consumption and reducing cache misses are important to reduce total energy consumption of embedded systems. Direct mapped caches consume much less power than that of same sized set associative caches but with a poor hit rate on average. Through experiments, we observe that memory space of direct mapped instruction caches is not used efficiently in most embedded applications. We design an efficient cache - a configurable instruction cache that can be tuned to utilize the cache sets efficiently for a particular application such that cache memory is exploited more efficiently by index remapping. Experiments on 11 benchmarks drawn from Mediabench show that the efficient cache achieves almost the same miss rate as a conventional two-way set associative cache on average and with total memory-access energy savings of 30% compared with a conventional two-way set associative cache.