Wormhole cut-through switching: Flit-level messages interleaving for virtual-channelless network-on-chip

A VLSI microrchitecture of a network-on-chip (NoC) router with a wormhole cut-through switching method is presented in this paper. The main feature of the NoC router is that, the wormhole messages\ud can be interleaved (cut-through) at flit-level in the same buffer pool and share communication links. Each flit belonging to the same message can track its routing paths correctly because a local identity-tag (ID-tag) is attached on each flit that varies over communication resources to support the wire-sharing\ud message transportation. Flits belonging to the same message will have the same local ID-tag on each\ud communication channel. The concept, on-chip microarchitecture, performance characteristics and interesting transient behaviors of the proposed NoC router that uses the wormhole cut-through switching method are presented in this paper. Routing engine module in the NoC architecture is an exchangeable module and must be designed in accordance with user specification i.e., static or adaptive routing algorithm. For quality of service purpose, inter-switch data transfers are controlled by using link-level overflow\ud control to avoid drops of data

Layered switching for networks on chip

We present and evaluate a novel switching mechanism called layered switching. Conceptually, the layered switching implements wormhole on top of virtual cut-through switching. To show the feasibility of layered switching, as well as to confirm its advantages, we conducted an RTL implementation study based on a canonical wormhole architecture. Synthesis results show that our strategy suggests negligible degradation in hardware speed (1%) and area overhead (7%). Simulation results demonstrate that it achieves higher throughput than wormhole alone while significantly reducing the buffer space required at network nodes when compared with virtual cut-through. Categories and Subject Descriptors: B.4 [Hardware]: Input/Output Data Communications