A Case for Small Row Buffers in Non-Volatile Main Memories

DRAM-based main memories have read operations that destroy the read data, and as a result, mustbuffer large amounts of data on each array access to keep chip costs low. Unfortunately, system-level trends such as increased memory contention in multi-core architectures and data mapping schemes that improve memory parallelism lead to only a small amount of the buffered data to be accessed. This makes buffering large amounts of data on every memory array access energy-inefficient; yet organizing DRAM chips to buffer small amounts of data is costly, as others have shown [11]. Emerging non-volatile memories (NVMs) such as PCM, STT-RAM, and RRAM, however, do not have destructive read operations, opening up opportunities for employing small row buffers without incurring additional area penalty and/or design complexity. In this work, we discuss and evaluate architectural changes to enable small row buffers at a low cost in NVMs. We find that on a multi-core system, reducing the rowbuffer size can greatly reduce main memory dynamic energy compared to a DRAM baseline with largerow sizes, without greatly affecting endurance, and for some NVM technologies, leads to improved performance.