CSC 456 Fall 2013/1d vb
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 |
Sources
- <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CE4QFjAA&url=http%3A%2F%2Fclasses.soe.ucsc.edu%2Fcmpe202%2FFall04%2Fpapers%2Fopteron.pdf&ei=hQsmUv6LKMnJsASb8IGACQ&usg=AFQjCNHvPcgDLJjfk0ufcd7HRA6aDAgU8w&sig2=fZvAhhwalsuZAs7GuamDHg&bvm=bv.51495398,d.cWc">link 1</a>
- http://en.wikipedia.org/wiki/Cray-1
- http://en.wikipedia.org/wiki/XK7
- https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDkQFjAB&url=http%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fdownload%3Fdoi%3D10.1.1.93.4333%26rep%3Drep1%26type%3Dpdf&ei=BwwmUtX-D7OgsQSrxYCgDw&usg=AFQjCNFrDohjVe-SefuaJvLAJwXEFVgWYw&sig2=Hfx9Gs6MI8XtOVT3PvoDlw&bvm=bv.51495398,d.cWc