Towards Ultra-High-Speed Cryogenic Single-Flux-Quantum Computing

Koki ISHIDA  Masamitsu TANAKA  Takatsugu ONO  Koji INOUE  

IEICE TRANSACTIONS on Electronics   Vol.E101-C   No.5   pp.359-369
Publication Date: 2018/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.359
Type of Manuscript: INVITED PAPER (Special Section on Innovative Superconducting Devices Based on New Physical Phenomena)
single flux quantum (SFQ),  cryogenic computing,  microprocessor,  cache memory,  Josephson junction,  low-power,  high-performance,  energy-efficient,  

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CMOS microprocessors are limited in their capacity for clock speed improvement because of increasing computing power, i.e., they face a power-wall problem. Single-flux-quantum (SFQ) circuits offer a solution with their ultra-fast-speed and ultra-low-power natures. This paper introduces our contributions towards ultra-high-speed cryogenic SFQ computing. The first step is to design SFQ microprocessors. From qualitatively and quantitatively evaluating past-designed SFQ microprocessors, we have found that revisiting the architecture of SFQ microprocessors and on-chip caches is the first critical challenge. On the basis of cross-layer discussions and analysis, we came to the conclusion that a bit-parallel gate-level pipeline architecture is the best solution for SFQ designs. This paper summarizes our current research results targeting SFQ microprocessors and on-chip cache architectures.