Architectural exploration of 3D FPGAs towards a better balance between area and delay

The emerging 3D technology, which stacks multiple dies within a single chip and utilizes through-silicon vias (TSVs) as vertical connections, is considered a promising solution for achieving better performance and easy integration. Similarly, a generic 2D FPGA architecture can evolve into a 3D one by extending its signal switching scheme from 2D to 3D by means of TSVs. However, replacing all 2D switch boxes (SBs) by 3D ones with full vertical connectivity is found both area-consuming and resource-squandering. Therefore, it is possible to greatly reduce the footprint with only minor delay increase by properly tailoring the structure and deployment strategy of 3D SB. In this paper, we perform a comprehensive architectural exploration of 3D FPGAs. Various architectural alternatives are proposed and then evaluated thoroughly to pick out the most appropriate ones with a better balance between area and delay. Finally, we recommend several configurations for generic 3D FPGA architectures, which can save up to 52% area with virtually no delay penalty.