CSC 456 Fall 2013/1d vb: Difference between revisions
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==Trends of Decreasing Pipeline Length== | ==Trends of Decreasing Pipeline Length== | ||
The issue with increased pipeline length is the problem of incorrect branch predictions. The longer a pipeline is, the more stages of wasted processing have been wasted when a different branch is taken. Decreasing the pipeline length has resulted in lower clock frequencies, but equal or better IPC. A smaller pipeline suffers less of a loss for every bad prediction, and the overall performance is improved. | |||
==An Example of Pipeline changes in Cray Systems== | ==An Example of Pipeline changes in Cray Systems== | ||
Revision as of 16:15, 3 September 2013
Trends in Pipelining
Trends of Increasing Pipeline Length
Trends of Decreasing Pipeline Length
The issue with increased pipeline length is the problem of incorrect branch predictions. The longer a pipeline is, the more stages of wasted processing have been wasted when a different branch is taken. Decreasing the pipeline length has resulted in lower clock frequencies, but equal or better IPC. A smaller pipeline suffers less of a loss for every bad prediction, and the overall performance is improved.
An Example of Pipeline changes in Cray Systems
| Year | Name | Pipeline Length | Number of Pipelines |
|---|---|---|---|
| 1976 | Cray 1 | 3 | 12 |
| 2012 | Cray XK7 | 12 for scalar , 17 for vector | 500 cabinets * 24 blades * 4 cores * 3 pipelines per chip |