First-Last: A Cost-Effective Adaptive Routing Solution for TSV-Based Three-Dimensional Networks-on-Chip

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.