Accelerating Communication in On-Chip Interconnection Networks

Abstract

Due to the ever-shrinking feature size in CMOS process technology, it is expected that future chip multiprocessors (CMPs) will have hundreds or thousands of processing cores. To support a massively large number of cores, packet-switched on-chip interconnection networks have become a de facto communication paradigm in CMPs. However, the on-chip networks have several drawbacks, such as limited on-chip resources, increasing communication latency, and insufficient communication bandwidth. In this dissertation, several schemes are proposed to accelerate communication in on-chip interconnection networks within area and cost budgets to overcome the problems. First, an early transition scheme for fully adaptive routing algorithms is proposed to improve network throughput. Within a limited number of resources, previously proposed fully adaptive routing algorithms have low utilization in escape channels. To increase utilization of escape channels, it transfers packets earlier before the normal channels are full. Second, a pseudo-circuit scheme is proposed to reduce network latency using communication temporal locality. Reducing per-hop router delay becomes more important for communication latency reduction in larger on-chip interconnection networks. To improve communication latency, the previous arbitration information is reused to bypass switch arbitration. For further acceleration, we also propose two aggressive schemes, pseudo-circuit speculation and buffer bypassing. Third, two handshake schemes are proposed to improve network throughput for nanophotonic interconnects. Nanophotonic interconnects have been proposed to replace metal wires with optical links in on-chip interconnection networks for low latency and power consumptions as well as high bandwidth. To minimize the average token waiting time of the nanophotonic interconnects, the traditional credit-based flow control is removed. Thus, the handshake schemes increase link utilization and enhance network throughput