Search

Phase Change Memory (PCM) is an emerging memory technology that has the capability to address the growing demand for memory capacity and bridge the gap between the main memory and the secondary storage. As a resistive memory, PCM is able to store data based on its resistance values. The wide resistance range of PCM makes it possible to store even multiple bits per cell (MLC) rather than a single bit per cell (SLC). Unfortunately, PCM cells suffer from short lifetime. That means PCM cells could tolerate a limited number of write operations, and afterward they tend to permanently stick at a constant value. Limited lifetime is an issue related to PCM memory; hence, in recent years, many studies have been conducted to prolong PCM lifetime. These schemes have vast variety and are applied at different architectural levels. In this survey, we review the important works of such schemes to give insights to those starting to research on non-volatile memories (NVMs). These schemes are not limited to PCM and are applicable on other NVM technologies due to the similarities between them and the generality of lifetime-prolonging schemes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]