Eliminating energy of same-content-cell-columns of on-chip SRAM arrays

Abstract

This work proposes to reduce energy by avoiding access to columns of on-chip SRAM arrays whose cell contents are all 1s or all 0s. We refer to this dynamic phenomenon as the Same-Cell-Content-Column (SCC-column). Analysis reveals that SCC-columns occur frequently in several processor arrays, such as tag arrays of L1 caches, TLBs and predictors. An interval based scheme that employs one bit per column is proposed to track whether we have a SCC-column. We explain how a SCC-column can be leveraged to reduce the energy needed for SRAM read and write accesses. Experimental analysis for a specific processor configuration reveals that the proposed scheme detects SCC-columns effectively. The potential energy savings of the proposed approach at 32nm often exceeds 40% for several processor arrays.