CTC: An end-to-end flow control protocol for multi-core systems-on-chip

• Published in: 2009 3rd ACM/IEEE International Symposium on Networks-on-Chip pp. 193 - 202
• Main Authors: Concer, N., Bononi, L., Soulie, M., Locatelli, R., Carloni, L.P.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2009
• Subjects: Communication system control; Control systems; Counting circuits; Delay; Multicore processing; Network interfaces; Network-on-a-chip; Protocols; Streaming media; System recovery
• ISBN: 1424441420; 9781424441426
• DOI: 10.1109/NOCS.2009.5071467

We propose Connection then Credits (CTC) as a new end-to-end flow control protocol to handle message-dependent deadlocks in networks-on-chip (NoC) for multicore systems-on-chip. CTC is based on the classic end-to-end credit-based flow control protocol but differs from it because it uses a network interface micro-architecture where a single credit counter and a single input data queue are shared among all possible communications. This architectural simplification reduces the area occupation of the network interfaces and increases their design reuse: for instance, the same network interface can be used to connect a core independently of the number of incoming and outgoing communications. CTC, however, requires a handshake preamble to initialize the credit counter in the sender network interface based on the buffering capacity of the receiver network interface. While this necessarily introduces a latency overhead in the transfer of a message, simulation-based experimental results show that the penalty in performance is limited when large messages need to be transferred, thus making CTC a valid solution for particular classes of applications such as video stream processing.