Cost-Effective Adaptive Routing

Cost-Effective Adaptive Routing

Abstract

3D integration opens up new opportunities for future multiprocessor chips by enabling fast and highly scalable 3D Network-on-Chip (NoC) topologies.

However, in an aim to reduce the cost of Through-silicon via (TSV), partially vertically connected NoCs, in which only a few vertical TSV links are available, have been gaining relevance.

To reliably route packets under such conditions, we introduce a lightweight, efficient and highly resilient adaptive routing algorithm targeting partially vertically connected 3D-NoCs named First-Last.

It requires a very low number of virtual channels (VCs) to achieve deadlock-freedom (2 VCs in the East and North directions and 1 VC in all other directions), and guarantees packet delivery as long as one healthy TSV connecting all layers is available anywhere in the network.

An improved version of our algorithm, named Enhanced-First-Last is also introduced and shown to dramatically improve performance under low TSV availability while still using less virtual channels than state-of-the-art algorithms.

A comprehensive evaluation of the cost and performance of our algorithms is performed to demonstrate their merits with respects to existing solutions.

CONCLUSION

We have presented a novel algorithm targeting partially vertically connected 3D-NoCs named First-Last, that guarantees packet delivery as long as one TSV pillar is available anywhere in the network.

Through a unique assignment of VCs, we have managed to avoid all the restrictions that related works impose on either the placement of the pillars, their selection during runtime, or both.

Moreover, we have shown, through Enhanced-First-Last, that by adding one VC in the vertical dimension, it was possible to dramatically boost the NoC’s performance in presence of few vertical connections, while still ensuring a lower implementation cost than state-of-the-art algorithms.

Both hardware synthesis and comprehensive cycle-accurate simulations were performed to demonstrate the merits of our routing approach.

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Cost-Effective Adaptive Routing