Smart computing on edge-devices has demonstrated huge potential for various application sectors such as personalized healthcare and smart robotics. These devices aim at bringing smart computing close to the source where the data is generated or stored, while coping with the stringent resource budget of the edge platforms. The conventional Von-Neumann architecture fails to meet these requirements due to various limitations e.g., the memory-processor data transfer bottleneck. Memristor-based Computation-In-Memory (CIM) has the potential to realize such smart edge computing for data-dominated Artificial Intelligence (AI) applications by exploiting both the inherent properties of the architecture and the physical characteristics of the memristors. This paper discusses different aspects of CIM, including classification, working principle, CIM potentials and CIM design-flow. The design-flow is illustrated through two case studies to demonstrate the huge potential of CIM in realizing orders of magnitude improvement in energy-efficiency as compared to the conventional architectures. Finally future challenges and research directions of CIM are covered.

Computation-in-memory using memristive devices is a promising approach to overcome the performance limitations of conventional computing architectures introduced by the von Neumann bottleneck which are also known as memory wall and power wall. It has been shown that accelerators based on memristive devices can deliver higher energy efficiencies and data throughputs when compared with conventional architectures. In the vast multitude of memristive devices, bipolar resistive switches based on the valence change mechanism (VCM) are particularly interesting due to their low power operation, non-volatility, high integration density and their CMOS compatibility. While a wide range of possible applications is considered, many of them such as artificial neural networks heavily rely on vector-matrix-multiplications (VMMs) as a mathematical operation. These VMMs are made up of large numbers of multiplication and accumulation (MAC) operations. The MAC operation can be realised using memristive devices in an analog fashion using Ohm’s law and Kirchhoff’s law. However, VCM devices exhibit a range of non-idealities, affecting the VMM performance, which in turn impacts the overall accuracy of the application. Those non-idealities can be classified into time-independent (programming variability) and time-dependent (read disturb and read noise). Additionally, peripheral circuits such as analog to digital converters can introduce errors during the digitalization. In this work, we experimentally and theoretically investigate the impact of device- and circuit-level effects on the VMM in a VCM crossbars. Our analysis shows that the variability of the low resistive state plays a key role and that reading in the RESET direction should be favored to reading in the SET direction.

In recent years, we are witnessing a trend toward in-memory computing for future generations of computers that differs from traditional von-Neumann architecture in which there is a clear distinction between computing and memory units. Considering that data movements between the central processing unit (CPU) and memory consume several orders of magnitude more energy compared to simple arithmetic operations in the CPU, in-memory computing will lead to huge energy savings as data no longer needs to be moved around between these units. In an initial step toward this goal, new non-volatile memory technologies, e.g., resistive RAM (ReRAM) and phase-change memory (PCM), are being explored. This has led to a large body of research that mainly focuses on the design of the memory array and its peripheral circuitry. In this article, we mainly focus on the tile architecture (comprising a memory array and peripheral circuitry) in which storage and compute operations are performed in the (analog) memory array and the results are produced in the (digital) periphery. Such an architecture is termed compute-in-memory-periphery (CIM-P). More precisely, we derive an abstract CIM-tile architecture and define its main building blocks. To bridge the gap between higher-level programming languages and the underlying (analog) circuit designs, an instruction-set architecture is defined that is intended to control and, in turn, sequence the operations within this CIM tile to perform higher-level more complex operations. Moreover, we define a procedure to pipeline the CIM-tile operations to further improve the performance. To simulate the tile and perform design space exploration considering different technologies and parameters, we introduce the fully parameterized first-of-its-kind CIM tile simulator and compiler. Furthermore, the compiler is technology-aware when scheduling the CIM-tile instructions. Finally, using the simulator, we perform several preliminary design space explorations regarding the three competing technologies, ReRAM, PCM, and STT-MRAM concerning CIM-tile parameters, e.g., the number of ADCs. Additionally, we investigate the effect of pipelining in relation to the clock speeds of the digital periphery assuming the three technologies. In the end, we demonstrate that our simulator is also capable of reporting energy consumption for each building block within the CIM tile after the execution of in-memory kernels considering the data-dependency on the energy consumption of the memory array. All the source codes are publicly available.

Memristive devices can be exploited for memory as well as logic operation paving the way for non von-Neumann Computation-In-Memory architectures. To validate the potential of such architectures accurate compact models for the memristive devices are required. As a standard device is not available, evaluating the performance of such an architecture is ambiguous. This paper proposes a flexible model for bipolar, filamentary switching, redox-based memristive devices. The model does catch both the device resistance ratio as well as the nonlinearity of the switching kinetics. It is used to perform design exploration for three memristive based circuit design (IMPLY, MAGIC and CRS) for computation-in-memory architectures.