Nimrod Wald

Memristor-Based Material Implication (IMPLY) Logic: Design Principles and Methodologies

Memristors are novel devices, useful as memory at all hierarchies. These devices can also behave as logic circuits. In this paper, the IMPLY logic gate, a memristor-based logic circuit, is described. In this memristive logic family, each memristor is used as an input, output, computational logic element, and latch in different stages of the computing process. The logical state is determined by the resistance of the memristor. This logic family can be integrated within a memristor-based crossbar, commonly used for memory. In this paper, a methodology for designing this logic family is proposed. The design methodology is based on a general design flow, suitable for all deterministic memristive logic families, and includes some additional design constraints to support the IMPLY logic family. An IMPLY 8-bit full adder based on this design methodology is presented as a case study.

MAGIC—Memristor-Aided Logic

Memristors are passive components with a varying resistance that depends on the previous voltage applied across the device. While memristors are naturally used as memory, memristors can also be used for other applications, including logic circuits. In this brief, a memristor-only logic family, i.e., memristor-aided logic (MAGIC), is presented. In each MAGIC logic gate, memristors serve as an input with previously stored data, and an additional memristor serves as an output. The topology of a MAGIC nor gate is similar to the structure of a common memristor-based crossbar memory array. A MAGIC nor gate can therefore be placed within memory, providing opportunities for novel non-von Neumann computer architectures. Other MAGIC gates also exist (e.g., and, or, not, and nand) and are described in this brief.

MRL — Memristor Ratioed Logic

Memristive devices are novel structures, developed primarily as memory. Another interesting application for memristive devices is logic circuits. In this paper, MRL (Memristor Ratioed Logic) - a hybrid CMOS-memristive logic family - is described. In this logic family, OR and AND logic gates are based on memristive devices, and CMOS inverters are added to provide a complete logic structure and signal restoration. Unlike previously published memristive-based logic families, the MRL family is compatible with standard CMOS logic. A case study of an eight-bit full adder is presented and related design considerations are discussed.

Memristor for computing: Myth or reality?

CMOS technology and its sustainable scaling have been the enablers for the design and manufacturing of computer architectures that have been fuelling a wider range of applications. Today, however, both the technology and the computer architectures are suffering from serious challenges/ walls making them incapable to deliver the right computing power at pre-defined constraints. This motivates the need of exploring new architectures and new technologies; not only to maintain the economic benefit of scaling, but also to enable the solutions of emerging computer power and data storage hungry applications such as big-data and data-intensive applications. This paper discusses the emerging memristor device as complementary (or alternative) to CMOS device and shows how this device can enable new ways of computing that will at least solve the challenges of todays architectures for some applications. The paper shows not only the potential of memristor devices in enabling new memory technologies and new logic design styles, but also their potential in enabling memory intensive architectures as well as neuromorphic computing due to their unique properties such as the tight integration with CMOS and the ability to learn and adapt.

Memristive logic: A framework for evaluation and comparison

Memristors have extended their influence beyond memory to logic and in-memory computing. Memristive logic design, the methodology of designing logic circuits using memristors, is an emerging concept whose growth is fueled by the quest for energy efficient computing systems. As a result, many memristive logic families have evolved with different attributes, and a mature comparison among them is needed to judge their merit. This paper presents a framework for comparing logic families by classifying them on the basis of fundamental properties such as statefulness, proximity (from the memory array), and flexibility of computation. We propose metrics to compare memristive logic families using analytic expressions for performance (latency), energy efficiency, and area. Then, we provide guidelines for a holistic comparison of logic families and set the stage for the evolution of new logic families.

Logic with Unipolar Memristors – Circuits and Design Methodology

Memristors are a general name for a set of emerging resistive switching technologies. These two terminal devices are characterized by a varying resistance, which is controlled by the voltage or current applied to them. The resistance state of a memristor is nonvolatile, and as such makes memristors attractive candidates for use as novel memory elements. Apart from their use for memory applications, the use of memristors in logic circuits is widely researched. A class of logic circuits named ‘stateful logic’, where the logic state of the inputs and outputs is stored in the form of resistance, is a promising approach for carrying out logic computations within memory. This chapter discusses the use of non-polar memristors, a type of memristors whose resistance depends only on the magnitude of the voltage across its terminals, for performing stateful logic operations. A design methodology is presented to allow structured development of stateful logic gates, and backed by a demonstration of the design process of OR and XOR gates using non-polar memristors.