Tuning Memory Fault Tolerance on the Edge

ABSTRACTError correction and fault tolerance have become pivotal considerations as conventional memories scale and emerging memories come to market. The common thread in these reliability challenges is that deep scaling reveals outliers in the memory system, which are responsible for the vast majority of faults. These cells, which may be attributed to process variation or undetected fabrication defects, tend to be more vulnerable to various forms of crosstalk, read- and write-disturbance, and even radiation-induced faults. By tracking faults in memory cells, identifying the worst offenders, and mitigating their effects accordingly, we can design dramatically improved fault tolerance techniques that are tuned to the fault characteristics of the memory at hand. A critical piece is the development of scalable and fault tolerance registries to track and retain critical information about these faults. The fault registries must be able to function in the faulty memory they protect, operate efficiently at the cell/bit-level, and handle extreme fault rates. Using the knowledge of faulty locations, our fault tolerance techniques applied to conventional main memories like DRAM and endurance-limited memories like flash and phase-change memory improve reliability, endurance, and lifetime by orders of magnitude while maintaining performance and energy efficiency.