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VLSI Design
Volume 2007 (2007), Article ID 46514, 13 pages
http://dx.doi.org/10.1155/2007/46514
Research Article

High-Performance Long NoC Link Using Delay-Insensitive Current-Mode Signaling

1Department of Information Technology, University of Turku, Turku 20014, Finland
2Turku Centre for Computer Science (TUCS), Turku 20520, Finland
3Research Council for Natural Sciences and Engineering, Academy of Finland, Helsinki 00501, Finland

Received 1 November 2006; Revised 24 January 2007; Accepted 1 March 2007

Academic Editor: Maurizio Palesi

Copyright © 2007 Ethiopia Nigussie et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

High-performance long-range NoC link enables efficient implementation of network-on-chip topologies which inherently require high-performance long-distance point-to-point communication such as torus and fat-tree structures. In addition, the performance of other topologies, such as mesh, can be improved by using high-performance link between few selected remote nodes. We presented novel implementation of high-performance long-range NoC link based on multilevel current-mode signaling and delay-insensitive two-phase 1-of-4 encoding. Current-mode signaling reduces the communication latency of long wires significantly compared to voltage-mode signaling, making it possible to achieve high throughput without pipelining and/or using repeaters. The performance of the proposed multilevel current-mode interconnect is analyzed and compared with two reference voltage mode interconnects. These two reference interconnects are designed using two-phase 1-of-4 encoded voltage-mode signaling, one with pipeline stages and the other using optimal repeater insertion. The proposed multilevel current-mode interconnect achieves higher throughput and lower latency than the two reference interconnects. Its throughput at 8 mm wire length is 1.222 GWord/s which is 1.58 and 1.89 times higher than the pipelined and optimal repeater insertion interconnects, respectively. Furthermore, its power consumption is less than the optimal repeater insertion voltage-mode interconnect, at 10 mm wire length its power consumption is 0.75 mW while the reference repeater insertion interconnect is 1.066 mW. The effect of crosstalk is analyzed using four-bit parallel data transfer with the best-case and worst-case switching patterns and a transmission line model which has both capacitive coupling and inductive coupling.