SMS-CAM: Shared matchline scheme for content addressable memory

Content addressable memory (CAM) is a hardware search engine (HSE) used for accelerating lookup functions in tagged cache, translation lookaside buffers (TLBs) and network routers. Despite its speedy search feature, augmentation of compare-evaluate blocks to storage units costs additional area. Activation of cells and matchlines (MLs) during search operations is responsible for huge dynamic-power dissipation. This paper proposes a shared ML scheme (SMS) based on a two-step evaluation CAM cell, in order to reduce ML transitions per word besides improving density in the comparison units. A 64 × 32-bit proposed SMS-CAM, using 45-nm CMOS technology, dissipates 1.06 fJ/bit/search and achieves 100.77-ps search time. At the cost of 6.55% sacrificial delay over a conventional CAM, the proposed CAM reduces 12.38% – 30.48% energy over a self-power off gating, the conventional and an early terminate ML precharge designs. Low energy-delay results better trade-off budget besides decreasing macro area in the SMS-CAM, which could be useful in search applications of network devices.