NS-FTR: A fault tolerant routing scheme for networks on chip with permanent and runtime intermittent faults

In sub-65nm CMOS technologies, interconnection networks-on-chip (NoC) will increasingly be susceptible to design time permanent faults and runtime intermittent faults, which can cause system failure. To overcome these faults, NoC routing schemes can be enhanced by adding fault tolerance capabilities, so that they can adapt communication flows to follow fault-free paths. A majority of existing fault tolerant routing algorithms are based on the turn model approach due to its simplicity and inherent freedom from deadlock. However, these turn model based algorithms are either too restrictive in the choice of paths that flits can traverse, or are tailored to work efficiently only on very specific fault distribution patterns. In this paper, we propose a novel fault tolerant routing scheme (NS-FTR) for NoC architectures that combines the North-last and South-last turn models to create a robust hybrid NoC routing scheme. The proposed scheme is shown to have a low implementation overhead and adapt to design time and runtime faults better than existing turn model, stochastic random walk, and dual virtual channel based routing schemes.