Butterfly-Fat-Tree topology based fault-tolerant Network-on-Chip design using particle swarm optimisation

Abstract

ABSTRACTAs the technology is scaling down more number of processing elements are integrated on to a single chip, namely system-on-chips (SoCs). Using traditional bus architecture in SoCs, communication among different processing elements is difficult. Hence, to overcome it, a new on-chip interconnection paradigm known as network-on-chip (NoC) has been proposed. The communication among different processing elements in NoCs is achieved using packet switching technique. In nano-scale era, NoCs are prone to vulnerable faults and designing an NoC to meet current application requirements is highly challenging. Hence, there is a need to develop reliable and efficient Fault-tolerant NoC designs. This paper presents a novel Fault-Tolerant NoC design for butterfly-fat-tree (BFT) topology with flexible spare core placement by taking different benchmark applications into consideration. The major challenge in fault-tolerant NoC is placement of spare core in the event of core failure in BFT network. Therefore, we have proposed an integer linear programming (ILP)-based exact method and particle swarm optimisation (PSO)-based meta-heuristic technique to place the spare core in a BFT network. Our major contribution is to place the spare core in BFT network such that system performance is improved in terms of communication cost, network latency, and router power consumption. Experimentations have been performed on several application benchmarks reported in the literature, (i) by varying the network size with fixed fault-percentage in the network, (ii) by varying the percentage of faults while fixing the network size and (iii) by taking multiple failed cores as a user input. We have compared overall communication cost obtained using our approaches with native fault-free approach. We have also compared overall communication cost and CPU runtime between ILP and PSO. The results show improvement in terms of overall communication cost, average network latency and network power consumption using our approaches compared to fault-free approach in BFT networks.