Design and Implementation of a Fully Asynchronous SFQ Microprocessor: SCRAM2

Author

Nobumori, Yusuke ; Nishigai, Takanobu ; Nakamiya, Kazunori ; Yoshikawa, Nobuyuki ; Fujimaki, Akira ; Terai, Hirotaka ; Yorozu, Shinich

Author_Institution

Yokohama Nat. Univ., Yokohama

Volume

17

Issue

2

fYear

2007

fDate

6/1/2007 12:00:00 AM

Firstpage

478

Lastpage

481

Abstract

A microprocessor test vehicle was developed for the investigation of asynchronous design methodology for rapid- single-flux-quantum (RSFQ) circuits. We have designed and implemented a fully asynchronous RSFQ microprocessor, named SCRAM2. The data-driven self-timing (DDST) architecture is used for the design of circuit blocks of the SCRAM2. In order to ensure the logical ordering between the circuit blocks, bit-serial handshaking was adopted. The performance of the handshaking system was enhanced based on the scalable-delay-insensitive (SDI) model. The SCRAM2 is an 8-bit bit-serial microprocessor with three-stage pipelining, with a basic microarchitecture similar to that of our previously designed synchronous microprocessor, CORE1alpha. The estimated average performance of the SCRAM2 is 577 MIPS using a logic simulation. We have implemented all circuit components using the SRL 2.5 kA/cm² Nb process and confirmed their correct operation. Several operations of the SCRAM2 have been successfully confirmed.

Keywords

asynchronous circuits; logic design; microprocessor chips; superconducting logic circuits; SCRAM2; asynchronous logic circuit; bit-serial handshaking; data-driven self-timing architecture; fully asynchronous RSFQ microprocessor; logic design; logic simulation; microarchitecture; rapid-single-flux-quantum circuit; scalable-delay-insensitive model; Binary decision diagrams; Circuit testing; Clocks; Design methodology; Digital systems; Josephson junctions; Microarchitecture; Microprocessors; Superconductivity; Timing; Asynchronous logic circuits; Josephson logic; SFQ circuit; superconducting integrated circuits;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/TASC.2007.898658

Filename

4277631