Phase-change memory: An architectural perspective

This article surveys the current state of phase-change memory (PCM) as a nonvolatile memory technology set to replace flash and DRAM in modern computerized systems. It has been researched and developed in the last decade, with researchers providing better architectural designs which address the technology's main challenges-its limited write endurance, potential long latency, high energy writes, power dissipation, and some concerns for memory privacy. Some physical properties of the technology are also discussed, providing a basis for architectural discussions. Also briefly shown are other architectural alternatives, such as FeRAM and MRAM. The designs surveyed in this article include read before write, wear leveling, write cancellation, write pausing, some encryption schemes, and buffer organizations. These allow PCM to stand on its own as a replacement for DRAM as main memory. Designs for hybrid memory systems with both PCM and DRAM are also shown and some designs for SSDs incorporating PCM.