Energy-Efficient Value Based Selective Refresh for Embedded DRAMS

DRAM idle power consumption consists for a large part of the power required for the refresh operation. This is exacerbated by (i) increasing amount of memory devoted to cache, that filters out many accesses to DRAM, and (ii) increased temperature of the chips, which increase leakage and thus data retention times. The well-known structured distribution of zeros in a memory, combined with the idea that cluster of cells containing all zeros in a DRAM do not have to be refreshed, can be constructively used together to reduce the unnecessary number of required refresh operations. We propose a value-based selective refresh scheme in which both horizontal and vertical clusters of zeros are identified and used to selectively deactivated refresh of such clusters. As a result, our technique significantly achieves a net reduction of the number of refresh operations on average of 31%, evaluated on a set of typical embedded applications.