Second-generation RISC floating point with multiply-add fused

Author

Hokenek, Erdem ; Montoye, Robert K. ; Cook, Peter W.

Author_Institution

IBM Thomas J. Watson Res. Center, Yorktown Heights, NY, USA

Volume

25

Issue

5

fYear

1990

fDate

10/1/1990 12:00:00 AM

Firstpage

1207

Lastpage

1213

Abstract

A 440000-transistor second-generation RISC (reduced instruction set computer) floating-point chip is described. The pipeline latency is only two cycles, and a double-precision result is produced every cycle. System throughput and accuracy are increased by using a floating-point multiply-add-fused unit, which carries out a double-precision accumulate as a two-cycle pipelined execution with only one rounding error. While the cycle time (40 ns) is competitive with other CMOS RISC systems, the floating-point performance stretches to the range of bipolar RISC systems (7.4-13 MFLOPS LINPACK). Leading zero anticipation makes the two-cycle pipeline possible by nearly eliminating the additional postnormalization time, and it allows for reduced overall system latency. Partial decode shifters allow complete time sharing for the multiply and data alignment. Improved design techniques for logarithmic addition and higher order counters for multiplication complete this second-generation RISC floating-point unit design

Keywords

CMOS integrated circuits; microprocessor chips; pipeline processing; reduced instruction set computing; 40 ns; 7.4 to 13 MFLOPS; RISC; double-precision accumulate; double-precision result; floating-point chip; higher order counters; logarithmic addition; multiplication; multiply-add-fused unit; partial decode shifters; pipeline latency; reduced instruction set computer; two-cycle pipelined execution; Adders; Circuits; Costs; Delay; Hardware; Pipelines; Reduced instruction set computing; Roundoff errors; Throughput; Very large scale integration;

fLanguage

English

Journal_Title

Solid-State Circuits, IEEE Journal of

Publisher

ieee

ISSN

0018-9200

Type

jour

DOI

10.1109/4.62143

Filename

62143