Low Static-Power Frequent-Value Data Caches

Abstract: Static energy dissipation in cache memories will constitute an increasingly larger portion of total microprocessor energy dissipation due to nanoscale technology characteristics and the large size of on-chip caches. We propose to reduce the static energy dissipation of an on-chip data cache by taking advantage of the frequent values (FV) that widely exist in a data cache memory. The original FV-based low-power cache design aimed at only reducing dynamic power, at the cost of a 5 % slowdown. We propose a better design that reduces both static and dynamic cache power, and that uses a circuit design that eliminates performance overhead. A designer can utilize our architecture by simulating an application and then synthesizing the FVs into an application-specific FV cache design when values will not change, or by simulating and then writing to an FV-cache with configuration registers when values could change. Furthermore, we describe hardware that can dynamically determine FVs and write to the configuration registers completely transparently. Experiments on 11 Spec 2000 benchmarks show that, in addition to the dynamic power savings, 33 % static energy savings for data caches can be achieved. 1