A Process-Variation-Adaptive Network-on-Chip with Variable-Cycle Routers and Variable-Cycle Pipeline Adaptive Routing

Yohei NAKATA  Hiroshi KAWAGUCHI  Masahiko YOSHIMOTO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E95-C   No.4   pp.523-533
Publication Date: 2012/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E95.C.523
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Solid-State Circuit Design – Architecture, Circuit, Device and Design Methodology)
Category: 
Keyword: 
network-on-chip,  process variation,  adaptive circuits,  routing algorithm,  

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Summary: 
As process technology is scaled down, a typical system on a chip (SoC) becomes denser. In scaled process technology, process variation becomes greater and increasingly affects the SoC circuits. Moreover, the process variation strongly affects network-on-chips (NoCs) that have a synchronous network across the chip. Therefore, its network frequency is degraded. We propose a process-variation-adaptive NoC with a variation-adaptive variable-cycle router (VAVCR). The proposed VAVCR can configure its cycle latency adaptively on a processor core basis, corresponding to the process variation. It can increase the network frequency, which is limited by the process variation in a conventional router. Furthermore, we propose a variable-cycle pipeline adaptive routing (VCPAR) method with VAVCR; the proposed VCPAR can reduce packet latency and has tolerance to network congestion. The total execution time reduction of the proposed VAVCR with VCPAR is 15.7%, on average, for five task graphs.