MRBS: An Area-Efficient Multicast Router for Network-on-Chip Using Buffer Sharing

Network-on-chip (NoC) has become the mainstream fabric architecture for chip multiprocessor (CMP) design. Owing to the market-driven advancement of modern applications in CMP, multicast traffic is aggressively increasing to support barrier synchronization, multithreading, and cache coherence protocols. Although multicast by branching of packets in the NoC router facilitates shortest path routing, additional branching-induced deadlocks must be circumvented. Existing NoC studies on deadlock-free minimal path routing in multicast traffic have typically deployed additional virtual channels or large buffers to hold entire packets, thereby significantly increasing the router area. Focusing on the area-efficient solution while sustaining the performance, we propose a novel multicast router using buffer sharing (MRBS) to guarantee deadlock-free multicast routing by exploiting the spatial diversity of the input buffer. MRBS ensures minimal path routing without requiring additional virtual channels or large buffers to hold entire packets. Extensive experiments were conducted by varying the buffer, packet, and network sizes, as well as the number of destinations per packet, under random multicast traffic with diverse injection rates. Simulation results show that MRBS achieves a 39.3 % improvement in the area-delay product on average for various network sizes compared to the conventional tree-based router.