The Connection-Then-Credit Flow Control Protocol for Heterogeneous Multicore Systems-on-Chip

• Published in: IEEE transactions on computer-aided design of integrated circuits and systems Vol. 29; no. 6; pp. 869 - 882
• Main Authors: Concer, Nicola, Bononi, Luciano, Soulie, Michael, Locatelli, Riccardo, Carloni, Luca P
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2010; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Communication system control; Computer aided design; Control systems; Counting circuits; Delay; Design engineering; End-to-end flow control; Flow control; message-dependent deadlock; Messages; Microarchitecture; Multicore processing; multicore systems-on-chip (SoC); network interface design; Network interfaces; Network-on-a-chip; Networks; networks-on-chip (NoC); Occupation; Protocols; Simplification; Streams; Studies; System recovery
• ISSN: 0278-0070; 1937-4151
• DOI: 10.1109/TCAD.2010.2048592

Connection-then-credits (CTC) is a novel end-to-end flow control protocol to handle message-dependent deadlocks in best-effort networks-on-chip (NoC) for embedded multicore systems-on-chip (SoCs). CTC is based on the classic end-to-end credit-based flow control protocol but differs from it because it uses a network interface microarchitecture 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.