Abstract-This paper presents the first synthesizable network-on-chip (NoC) based on a mesh topology, which supports adaptive and deadlock-free tree-based multicast routing without virtual channels. The deadlock-free routing algorithms for unicast and multicast packets are the same. Therefore, the routing function gate-level implementation is very efficient. Multicast packets are injected to the network by sending multiple packet headers beforehand. The packet headers contain destination addresses to set up multicast trees connecting a source with multiple destination nodes. An additional locally uniform identification (ID) field is packetized together with flits belonging to the same packet. Therefore, flits of different unicast or multicast packets can be interleaved in the same queue because of the local ID-tags, which are updated and mapped dynamically to support bandwidth scalability of interconnection links. Deadlocks in tree-based multicast routing are handled using a flit-by-flit round arbitration and a fair hold-release tagging mechanism. The effectiveness of the novel mechanism has been experimented under multiple multicast conflicts scenarios, where the experimental results show that all traffic is accepted in-order and lossless in their destination nodes even if adaptive routing functions are used and the sizes of the multicast messages are very long.Index Terms-Network-on-chip (NoC), tree-based multicast routing, synchronous parallel pipeline, wormhole packet switching.

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Abstract-A new theory for deadlock-free multicast routing especially used for on-chip interconnection network (NoC) is presented in this paper. The NoC router hardware solution that enables the deadlock-free multicast routing without utilizing virtual channels is introduced formally. The special characteristic of the NoC is that, wormhole packets can cut-through at flit-level and can be interleaved in the same channel with other flits of different packets by multiplexing it using a rotating flit-by-flit arbitration. The routing paths of each flit can be guaranteed correct because flits belonging to the same packet are labeled with the same local Id-tag on every communication channel. Hence, multicast deadlock problem can be solved at each router by further applying a hold-release tagging mechanism to control and manage conflicting multicast requests.Index Terms-Network-on-chip, tree-based and multipath-based multicast routing, Id-tag-based wormhole packet switching, runtime adaptive routing and scheduling.

Abstract-This paper presents adaptive routing selection strategies suitable for network-on-chip (NoC). The main prototype presented in this paper uses contention information and bandwidth space occupancy to make routing decision at runtime during application execution time. The performance of the NoC router is compared to other NoC routers with queue-length-oriented adaptive routing selection strategies. The evaluation results show that the contention-and bandwidth-aware adaptive routing selection strategies are better than the queue-length-oriented adaptive selection strategies. Messages in the NoC are switched with a wormhole cut-through switching method, where different messages can be interleaved at flit-level in the same communication link without using virtual channels. Hence, the head-of-line blocking problem can be solved effectively and efficiently. The routing control concept and the VLSI microarchitecture of the NoC routers are also presented in this paper.

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