Abstract:

Exploiting nonuniform distribution of cache accesses among sets, VWay cache allows varying ways in sets according to the runtime demands and outperforms conventional setassociative cache in resource utilization. However, the tag array in VWay cache is expanded, inducing large area and power overhead. Considering that the tag array is underutilized in VWay cache, we propose a lowoverhead heterogeneous variable way cache, named HVWay cache. The HVWay cache adopts a heterogeneous tag array and cut down the capacity of tag ways by sets sharing in the same way. Maintaining tag replacement information in perset granularity, The HVWay cache selects the least recently used tag entries for eviction. Experiment results of Cacti and Simics simulators show that the HVWay cache brings down the latency, area and power overhead greatly at the expense of small performance loss.

Key words: cache;lowoverhead;heterogeneous organization;replacement strategy