Minimal Maximum-Level Programming: Faster memory access via multi-level cell sharing

Abstract

In multi-level-cell (MLC) memory such as Flash and Phase-change memory, shrinking cell size and the growing number of levels per cell worsen the access-rate to capacity ratio and even reduce access rate. We present Minimal Maximum-Level Programming (MMLP), a scheme for expediting cell writing by sharing physical cells among multiple data pages and exploiting the fact that making moderate changes to a cell's level is faster than making large ones. Reading is also expedited by requiring fewer reference comparisons. In a four-level cell example, we achieve a 32% reduction in write/read latency relative to prior art with negligible area overhead.