Stateful Logic using Phase Change Memory

TL;DR

This paper introduces a novel method for implementing stateful logic using phase change memory (PCM), demonstrating four logic gates experimentally, which enables in-memory processing and enhances computational efficiency.

Contribution

The paper presents the first experimental demonstration of stateful logic gates using PCM, differing from prior resistive memory approaches, and shows their potential for in-memory computing systems.

Findings

Successfully demonstrated four PCM-based logic gates (NOR, IMPLY, OR, NIMP)

Proved that PCM-based stateful logic forms a complete set for universal computation

Enabled sequential execution of any logic function within PCM memory arrays

Abstract

Stateful logic is a digital processing-in-memory technique that could address von Neumann memory bottleneck challenges while maintaining backward compatibility with standard von Neumann architectures. In stateful logic, memory cells are used to perform the logic operations without reading or moving any data outside the memory array. Stateful logic has been previously demonstrated using several resistive memory types, mostly by resistive RAM (RRAM). Here we present a new method to design stateful logic using a different resistive memory - phase change memory (PCM). We propose and experimentally demonstrate four logic gate types (NOR, IMPLY, OR, NIMP) using commonly used PCM materials. Our stateful logic circuits are different than previously proposed circuits due to the different switching mechanism and functionality of PCM compared to RRAM. Since the proposed stateful logic form a functionally complete set, these gates enable sequential execution of any logic function within the memory, paving the way to PCM-based digital processing-in-memory systems.