Ripple-precharge TCAM: a low-power solution for network search engines

Abstract

A novel low power ripple-precharge ternary CAM (RP-TCAM) architecture is proposed for applications in longest prefix matching tasks. The main motivation behind this research is to reduce the dynamic power consumption in TCAM due to frequent charging and discharging of the highly capacitive match line. This issue is addressed by exploiting the fact that when we compare only the first four bits of incoming packet's destination address we can identify up to 80% mismatches in the forwarding table. A selective precharge scheme was devised exploiting the above fact wherein the match line is charged only when there is an exact match in the first four bits of TCAM word, thereby significantly reducing the number of transitions in the match line. The parasitics for simulation were extracted from the layout implemented for a 64 /spl times/ 32 RP-TCAM architecture using 0.18/spl mu/m technology. This structure has 1.71% less area and 80% less power when compared to the conventional TCAM of equal storage size and functionality. Our RP-TCAM architecture has a search time of 1.86ns.