A Nonvolatile Associative Memory-Based Context-Driven Search Engine Using 90 nm CMOS/MTJ-Hybrid Logic-in-Memory Architecture

Abstract

This paper presents algorithm, architecture, and fabrication results of a nonvolatile context-driven search engine that reduces energy consumption as well as computational delay compared to classical hardware and software-based approaches. The proposed architecture stores only associations between items from multiple search fields in the form of binary links, and merges repeated field items to reduce the memory requirements and accesses. The fabricated chip achieves <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$13.6\times$</tex> </formula> memory reduction and 89% energy saving compared to a classical field-based approach in hardware, based on content-addressable memory (CAM). Furthermore, it achieves <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$8.6\times$</tex> </formula> reduced number of clock cycles in performing search operations compared to the CAM, and five orders of magnitude reduced number of clock cycles compared to a fabricated and measured ultra low-power CPU-based counterpart running a classical search algorithm in software. The energy consumption of the proposed architecture is on average three orders of magnitude smaller than that of a software-based approach. A magnetic tunnel junction (MTJ)-based logic-in-memory architecture is presented that allows simple routing and eliminates leakage current in standby using 90 nm CMOS/MTJ-hybrid technologies.