Headfirst sliding routing: A time-based routing scheme for bus-NoC hybrid 3-D architecture

A contact-less approach that connects chips in vertical dimension has a great potential to customize components in 3-D chip multiprocessors (CMPs), assuming card-style components inserted to a single cartridge communicate each other wirelessly using inductive-coupling technology. To simplify the vertical communication interfaces, static Time Division Multiple Access (TDMA) is used for the vertical broadcast buses, while arbitrary or customized topologies can be used for intra-chip networks. In this paper, we propose the Headfirst sliding routing scheme to overcome the simple static TDMA-based vertical buses. Each vertical bus grants a communication time-slot for different chips at the same time periodically, which means these buses work with different phases. Depending on the current time, packets are routed toward the best vertical bus (elevator) just before the elevator acquires its communication time-slot. Network simulations show that Headfirst sliding routing reduces the communication latency by up to 32.7%, and full-system CMP simulations show that it reduces application execution time by 9.9%. Synthesis results show that the area and critical path delay overheads are modest.