How Useful Are Non-Blocking Loads, Stream Buffers and Speculative Execution in Multiple Issue Processors?

  • Authors:

  • K. I. Farkas;N. P. Jouppi;P. Chow

  • Affiliations:

  • -;-;-

  • Venue:
  • HPCA '95 Proceedings of the 1st IEEE Symposium on High-Performance Computer Architecture
  • Year:
  • 1995

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Abstract

We investigate the relative performance impact of non-blocking loads, stream buffers, and speculative execution both used individually and in conjunction with each other. We have simulated the SPEC92 benchmarks on a statically scheduled quad-issue processor model, running code from the Multiflow compiler. Non-blocking loads and stream buffers both provide a significant performance advantage, and their combination performs significantly better than either alone. For example, with a 64-byte, 2-way set associative cache with 32 cycle fetch latency, non-blocking loads reduce the run-time by 21% while stream-buffers re-duce it by 26%, and the combined use of the two yields a 47% reduction. The addition of speculative execution further improves the performance of the systems that we have simulated, with or without non-blocking loads and stream buffers, by an additional 20% to 40%. We expect that the use of all three of these techniques will be important in future generations of microprocessors.