I-cache configurability for temperature reduction through replicated cache partitioning

On-chip caches have been known to be a major contributor to leakage power as they occupy a sizable fraction of the chip's real estate and as such have been the target of power optimization techniques. However, many of these techniques do not consider the effects of temperature on leakage power and can hence be suboptimal since leakage power rises rapidly with temperature. When large fractions of the cache are disabled and only a small partition is used, the power density increases significantly which leads to increased temperature and leakage. We propose a temperature reduction methodology that leverages recently introduced configurable caches, in order to not only assign to the task a cache partition commensurate to its current demand but also to minimize the associated power density and temperature. In order to counteract the effect of elevated power density and achieve temperature reductions, in the proposed technique each such cache partition is replicated and only one of the replicas is active at any time. The inactive partition replicas are placed into a low-power drowsy mode while the primary partition services the task's instruction requests. By periodically switching the tasks association between replica cache partitions, the power density and hence the temperature are reduced.