A Novel Energy Efficient Multicasting Approach For Mesh NoCs

Network on Chip (NoC) is a scalable and flexible communication infrastructure which replaces dedicated point to point wiring between cores on a chip. Communication among the cores is established via routers interfaced to each core. Efficiency of NoC router plays an important role in determining the performance of the underlying network in multicore systems. In Chip Multiprocessors (CMP), cache coherence protocols, and cache miss reply from memory controller uses multicast communication. In early days, multicast communication is achieved by generating multiple unicast packets. The multicast message efficency can be improved by providing support at the hardware level. Multicast communication can be optimised by grouping destination cores of a multicast message into various partitions. Existing state of the art multicasting techniques on NoC issue one packet each to each destination partition, there by avoiding need for multiple unicast packets. In this paper, we propose an efficient multicast approach for 2D Mesh NoCs where a single packet issued from the source core, move through network as much as possible and then create duplicate packet as and when required. Experimental results show that our technique significantly reduces average multicast transaction latency and number of link traversals required to realise a multicast communication. This reduction in latency and link activity gives significant energy savings associated with multicast communication.