Yoda: Judge Me by My Size, Do You?

Abstract

Phase change memory is a promising alternative to conventional memories such as DRAM due to its density and non-volatility. Unfortunately, reliability is still a challenge as limited write endurance, exacerbated by process variation, leads to increasing numbers of stuck-at faults over the memory's lifetime. Error-correcting Pointers (ECP) is a popular proposal to mitigate stuck-at faults by recording the addresses and the values of faulty bits in order to extend the memory lifetime. In this paper, we propose Yoda, a method to extend ECP with one or a small number of additional encoding bits in order to dramatically improve the effectiveness and guaranteed fault correction capability of ECP. Our simulation results demonstrate that Yoda has a 3.0x improvement in fault coverage compared to a fault-aware ECP with a similar overhead, while also providing a 2.5-3.0x improvement over state-of-the-art schemes with comparable complexity.