Agner`s CPU blog

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Test results for Intel's Sandy Bridge processor
Author: Agner Date: 2015-12-22 01:42
This is interesting. I can see this warm-up behavior on an Intel Skylake i7-6700. It seems to use the lower 128-bit lane twice for 256-bit instructions during a warm-up period of 14 µs before the 256-bit instructions can run at full speed. It goes back to the cold state after 675 µs of no 256-bit instructions.

I have never seen this behavior on any other processor. It would be interesting to know which processors have this behavior and which ones have not.

 
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