MORSE: Memory Overwrite Time Guided Soft Writes to Improve ReRAM Energy and Endurance

ReRAM is an attractive main memory technology due to its high density and low idle power. However, ReRAM exhibits costly writes, especially in terms of energy and endurance. Prior device studies show that retention can be traded off for write energy and endurance by employing soft write operations with lower currents. But given their reduced retention times, soft writes require refresh operations to prevent data loss. Unfortunately, a large number of refreshes are needed in between writes to infrequently updated data. Hence, a non-volatile memory system with soft writes still needs traditional hard writes, and a way to choose between them.