PROTON: An automatic place-and-route tool for optical networks-on-chip

Optical Networks-on-Chip (ONoCs) are considered a promising way of improving power and bandwidth limitations in next generation multi- and many-core integrated systems. Today, most related research acknowledges the key role of the physical layer in assessing ONoC topologies (e.g., insertion loss), but overlooks the placement and routing stage in the design process, hence applying physical design considerations to topology logic schemes. Such a mismatch is fundamentally due to the lack of mature CAD tools for placement and routing of optical NoCs. The objective of this work is to bridge this gap: We propose PROTON, a fast tool for automatic placement and routing of ONoC topologies, which can support designers in quantifying the degradation of design quality metrics when moving from topology logic schemes to their physical implementation. This gap is especially relevant for Wavelength-Routed ONoCs (WRONoCs), where logic schemes typically make unrealistic assumptions about the placement of initiators and targets. For this reason, we put PROTON to work with the most promising WRONoC topologies and explore their physical design space given the placement and routing constraints of a 3D stacked system. We also compare automatically generated layouts with handcrafted ones reported in the literature for the same topologies and target system, and prove an insertion loss improvement by up to 150x. With PROTON the exploration of the physical design space of ONoC topologies is possible as well as their scalability analysis considering the layout.