Replacing global wires with an on-chip network

Abstract

This paper explores the power implications of replacing global chip wires with an on-chip network. The authors optimized the network links by varying repeater spacing, link pipelining, and voltage scaling, to significantly reduce the energy to send a bit across chip. An analytic model of large chip designs with an on-chip two-dimensional mesh network was developed and the power savings possible in a 70 nm process for two different design points: a circuit-switched ASIC or FPGA design, and a dynamic packet-switched tiled architecture were estimated. For circuit-switched networks, achievable power savings are 35-50% for a mesh with 1 mm links. The packet switched designs use multiplexing and signal encoding to reduce the number of link wires required, but the router overhead limits peak wire power savings to around 20% with optimal tile sizes of around 2 mm.