Dynamic Ternary Content-Addressable Memory Is Indeed Promising: Design and Benchmarking Using Nanoelectromechanical Relays

TL;DR

This paper introduces a novel low-power dynamic TCAM design using nanoelectromechanical relays, achieving higher density and energy efficiency compared to traditional SRAM, RRAM, and FeFET TCAMs.

Contribution

It proposes a new TCAM architecture with NEM relays and one-shot refresh, significantly improving density and energy efficiency over existing designs.

Findings

Occupies only 3 transistors per cell, outperforming 16-transistor SRAM TCAM.

Improves write energy efficiency by up to 131 times over RRAM.

Enhances search energy-delay-product by up to 12.7 times over SRAM.

Abstract

Ternary content addressable memory (TCAM) has been a critical component in caches, routers, etc., in which density, speed, power efficiency, and reliability are the major design targets. There have been the conventional low-write-power but bulky SRAM-based TCAM design, and also denser but less reliable or higher-write-power TCAM designs using nonvolatile memory (NVM) devices. Meanwhile, some TCAM designs using dynamic memories have been also proposed. Although dynamic design TCAM is denser than CMOS SRAM TCAM and more reliable than NVM TCAM, the conventional row-by-row refresh operations land up with a bottleneck of interference with normal TCAM activities. Therefore, this paper proposes a custom low-power dynamic TCAM using nanoelectromechanical (NEM) relay devices utilizing one-shot refresh to solve the memory refresh problem. By harnessing the unique NEM relay characteristics with a proposed novel cell structure, the proposed TCAM occupies a small footprint of only 3 transistors (with two NEM relays integrated on the top through the back-end-of-line process), which significantly outperforms the density of 16-transistor SRAM-based TCAM. In addition, evaluations show that the proposed TCAM improves the write energy efficiency by 2.31x, 131x, and 13.5x over SRAM, RRAM, and FeFET TCAMs, respectively; The search energy-delay-product is improved by 12.7x, 1.30x, and 2.83x over SRAM, RRAM, and FeFET TCAMs, respectively.