A Resistive TCAM Accelerator for Data-Intensive Computing

Power dissipation and off-chip bandwidth restrictions are critical challenges that limit microprocessor performance. Ternary content addressable memories (TCAM) hold the potential to address both problems in the context of a wide range of data-intensive workloads that benefit from associative search capability. Power dissipation is reduced by eliminating instruction processing and data movement overheads present in a purely RAM based system. Bandwidth demand is lowered by processing data directly on the TCAM chip, thereby decreasing off-chip traffic. Unfortunately, CMOS-based TCAM implementations are severely power- and area-limited, which restricts the capacity of commercial products to a few megabytes, and confines their use to niche networking applications. This paper explores a novel resistive TCAM cell and array architecture that has the potential to scale TCAM capacity from megabytes to gigabytes. High-density resistive TCAM chips are organized into a DDR3-compatible DIMM, and are accessed through a software library with zero modifications to the processor or the motherboard. On applications that do not benefit from associative search, the TCAM DIMM is configured to provide ordinary RAM functionality. By tightly integrating TCAM with conventional virtual memory, and by allowing a large fraction of the physical address space to be made content-addressable on demand, the proposed memory system improves average performance by 4x and average energy consumption by 10x on a set of evaluated data-intensive applications.