Galaxy: A high-performance energy-efficient multi-chip architecture using photonic interconnects

Yigit Demir, Yan Pan, Seukwoo Song, Nikos Hardavellas, John Kim, Gokhan Memik

Research output: Chapter in Book/Report/Conference proceedingConference contribution

29 Scopus citations


The scalability trends of modern semiconductor technology lead to increasingly dense multicore chips. Unfortunately, physical limitations in area, power, off-chip bandwidth, and yield constrain single-chip designs to a relatively small number of cores, beyond which scaling becomes impractical. Multi-chip designs overcome these constraints, and can reach scales impossible to realize with conventional single-chip architectures. However, to deliver commensurate performance, multi-chip architectures require a cross-chip interconnect with bandwidth, latency, and energy consumption well beyond the reach of electrical signaling. We propose Galaxy, an architecture that enables the construction of a many-core "virtual chip" by connecting multiple smaller chiplets through optical fibers. The low optical loss of fibers allows the flexible placement of chiplets, and offers simpler packaging, power, and heat requirements. At the same time, the low latency and high bandwidth density of optical signaling maintain the tight coupling of cores, allowing the virtual chip to match the performance of a single chip that is not subject to area, power, and bandwidth limitations. Our results indicate that Galaxy attains speedup of 2.2x over the best single-chip alternatives with electrical or photonic interconnects (3.4x maximum), and 2.6x smaller energy-delay product (6.8x maximum). We show that Galaxy scales to 4K cores and attains 2.5x speedup at 6x lower laser power compared to a Macrochip with silicon waveguides.

Original languageEnglish (US)
Title of host publicationICS 2014 - Proceedings of the 28th ACM International Conference on Supercomputing
PublisherAssociation for Computing Machinery
Number of pages10
ISBN (Print)9781450326421
StatePublished - 2014
Event28th ACM International Conference on Supercomputing, ICS 2014 - Munich, Germany
Duration: Jun 10 2014Jun 13 2014

Publication series

NameProceedings of the International Conference on Supercomputing


Other28th ACM International Conference on Supercomputing, ICS 2014


  • energy efficiency
  • interconnection networks
  • nanophotonics

ASJC Scopus subject areas

  • Computer Science(all)


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