Optimal distribution of privileged nodes in networks-on-chip

With ongoing technology scaling, networks-on-chip will have to be organized hierarchically in order to cope with their growing size. Privileged nodes carry out dedicated tasks essential to establish and coordinate proper functionality within and among hierarchical units. In order to mitigate the impact of a privileged node´s failure, redundancy has to be established by a suitable distribution of privileged nodes. This contribution presents an integer linear programming (ILP) formulation for finding distributions that minimize hardware cost under redundancy constraints or maximize redundancy for given cost for arbitrary NoC topologies. For mesh and mesh torus, optimal solutions are obtained with up to 289 nodes. For larger regular networks, a technique based on the generation and assembly of regular tiles is proposed. A characterization of the conditions for optimality of tile-based networks is provided.