Black-bus: A new data-transfer technique using local address on networks-on-chips

Network-on-a-Chip (NoC) has received attention as a high-performance interconnect, because traditional buses, which can't transfer more than one data-stream simultaneously, are more likely to become a bottleneck. Since some concepts of NoC have been proposed by simply borrowing the networking structure of parallel computers or System Area Networks (SANs), it tends to require complicated network interface logic in all the nodes. In this paper, we propose a novel data-transfer method called Black-Bus as an NoC. In Black-Bus, a local identifier (ID) is attached to each raw data as routing information. Unlike the traditional packet transfer, the local ID is transferred on dedicated wires attached to data lines to remove complicated packet generation procedure in a node. Only a small-sized local ID is required to specify routing tags to the destination, and intermediate routers change it to solve local ID conflicts between paths on a physical channel. The required local ID and routing table sizes for the Black-Bus router are evaluated with access trace data of NAS Parallel Benchmarks for on-chip multiprocessors, and JPEG codec as stream processing. Evaluation results show that most of the applications require only at most 3 bits for the local ID in a 16-node system. And the Black-Bus data-transfer reduces up to 75% of routing tags compared with global addressing scheme used in the traditional packet networks.