Energy efficient Frequent Value data Cache design

Recent work has shown that a small number of distinct frequently occurring values often account for a large portion of memory accesses. In this paper we demonstrate how this frequent value phenomenon can be exploited in designing a cache that trades off performance with energy efficiency. We propose the design of the Frequent Value Cache (FVC) in which storing a frequent value requires few bits as they are stored in encoded form while all other values are stored in unencoded form using 32 bits. The data array is partitioned into two arrays such that if a frequent value is accessed only the first data array is accessed; otherwise an additional cycle is needed to access the second data array. Experiments with some of the SPEC95 benchmarks show that on an average a 64 Kb/64-value FVC provides 28.8% reduction in Ll cache energy and 3.38% increase in execution time delay over a conventional 64 Kb cache.