Instruction Issue Logic in Pipelined Supercomputers

Shlomo Weiss, James E. Smith

Research output: Contribution to journalArticlepeer-review


Basic principles and design tradeoffs for control of pipelined processors are first discussed. We concentrate on register-register architectures like the CRAY-1 where pipeline control logic is localized to one or two pipeline stages and is referred to as “instruction issue logic;” Design tradeoffs are explored by giving designs for a variety of instruction issue methods that represent a range of complexity and sophistication. These vary from the CRAY-1 issue logic to a version of Tomasulo’s algorithm, first used in the IBM 360/91 floating point unit. Also studied are Thornton’s “scoreboard” algorithm used on the CDC 6600 and an algorithm we have devised. To provide a standard for comparison, all the issue methods are used to implement the CRAY-1 scalar architecture. Then, using a simulation model and the Lawrence Livermore Loops compiled with the CRAY Fortran compiler, performance results for the various issue methods are given and discussed.

Original languageEnglish
Pages (from-to)1013-1022
Number of pages10
JournalIEEE Transactions on Computers
Issue number11
StatePublished - Nov 1984
Externally publishedYes


  • CDC 6600 scoreboard
  • CRAY-1
  • IBM 360/91
  • Tomasulo’s algorithm
  • control logic
  • instruction issue logic
  • performance simulation
  • pipelined computers
  • supercomputers


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