IMEC: A Fully Morphable In-Memory Computing Fabric Enabled by Resistive Crossbar

Abstract

In this paper, we propose a fully morphable In-MEmory Computing (IMEC) fabric to better implement the concept of processing inside memory (PIM). Enabled by emerging nonvolatile memory, i.e., RRAM and its monolithic 3D integration, IMEC can be configured into one or a combination of four distinct functions, 1) logic, 2) ternary content addressable memory, 3) memory, and 4) interconnect. Thus, IMEC exploits a continuum of PIM capabilities across the whole spectrum, ranging from 0 percent (pure data storage) to 100 percent (pure compute engine), or intermediate states in between. IMEC can be modularly integrated into the DDRx memory subsystem, communicating with processors by the ordinary DRAM commands. Additionally, to reduce the programming burden, we provide a complete framework to compile applications written in high-level programming language (e.g., OpenCL) onto IMEC. This framework also enables code portability across different platforms for heterogeneous computing. By using this framework, several benchmarks are mapped onto IMEC for evaluating its performance, energy and resource utilization. The simulation results show that, IMEC reduces the energy consumption by 99.6 percent, and achieves $644\times$ speedup, compared to a baseline CPU system. We further compare IMEC with FPGA architecture, and demonstrate that the performance improvement is not simply obtained by replacing SRAM cells with denser RRAM cells.