NoCs with Combined Low and High Priority Wormhole Packet Delivery Services

Abstract:
A synchronous parallel pipeline network-on-chip using wormhole packet switching and supporting guaranteed-completion best-effort with low (LP) and high priority (HP) wormhole packet delivery service is presented in this paper. Both our proposed LP and HP message services deliver a good quality of service in term of lossless packet completion and in-order message data delivery. However, the LP message service does not guarantee minimal completion bound. The HP packets will absolutely use 100% bandwidth of their reserved links, and are suitable for small size messages (less than hundred bytes), otherwise the other HP and LP messages, which require also the links, will experience relatively high latency depending on the size of the HP message. The LP packets are routed using a minimal adaptive routing, while the HP packets are routed using a non-minimal adaptive routing algorithm. Therefore, an additional 3-bit field, identifying the packet type, is introduced in their packet headers to classify and to determine the type of service committed to the packet. Our NoC prototypes have been also synthesized using a CMOS standard-cell technology to evaluate the cost of implementing the combination of both services.