Wear leveling for crossbar resistive memory

Abstract

Resistive Memory (ReRAM) is an emerging non-volatile memory technology that has many advantages over conventional DRAM. ReRAM crossbar has the smallest 4F2 planar cell size and thus is widely adopted for constructing dense memory with large capacity. However, ReRAM crossbar suffers from large sneaky currents and IR drop. To ensure write reliability, ReRAM write drivers choose larger than ideal write voltages, which over-SET/over-RESET many cells at runtime and lead to severely degraded chip lifetime. In this paper, we propose XWL, a novel table based wear leveling scheme for ReRAM crossbars. We study the correlation between write endurance and voltage stress in ReRAM crossbar. By estimating and tracking the effective write stress to different rows at runtime, XWL chooses the ones that are stressed the most to mitigate. Our experimental results show that, on average, XWL improves the ReRAM crossbar lifetime by 324% over the baseline, with only 6.1% performance overhead.