Emerging Memory Structures for VLSI Circuits

Ever since the emergence of the electrical computer and the Von Neumann model, computer architects have adhered to a well-structured hierarchy of memory solutions, clearly trading off performance and capacity with cost. The ubiquitous memory technologies, dominated by SRAM, DRAM, Flash, and magnetic hard disks, are each situated in a well-defined location within this hierarchy. However, as processes have scaled into deep nanometer feature sizes and the demand for larger capacities and bandwidths increases, these traditional options face tough challenges and may be limited in their ability to continue to provide the new requirements. New technologies, such as phase change memory (PCM), magnetic RAM (MRAM), and resistive RAM (RRAM), have been researched and developed over the recent past in an attempt to meet these demands and replace some or all of the traditional technologies. In this article, the primary technologies are overviewed, including those that currently fill the memory hierarchy pyramid, the primary candidates to join or replace them in the near-term, and a number of newer candidates that may arise as legitimate solutions in the farther term. In addition, an overview of the current state of processing within the emerging memory technologies is provided, as an attempt to break free of the traditional Von Neumann paradigm to overcome the energy and performance bottlenecks in modern systems.