I found the following issue with Blender render.

When I render an image after a fresh restart, it uses 100% CPU and finish in about 5-7 minutes.

But after a few renders, the same image will render in 43 minutes and use only 40% CPU

I think it is caused if I open more than 1 blender instance.

The only solution I found is a restart.

I have win 10.


After much research I found this is a win 10 issue, that is happening not only when running blender, I install MAC and the problem is solved.


This isn't really a problem with Blender that could be fixed, most likely it's just that the computer, after being used for a while, heats up. It also depends on how many things you are running at the same time.

  • $\begingroup$ correct, this is a Windows issue - I have dual boot, and the problem doesn't happen with MAC $\endgroup$ – Elia Weiss Sep 5 '17 at 6:38

You can give blender process high priority in task menager. Go to task menager > details then find the blender.exe process and right click on it. Now you can choose "set priority" and check for example high. It may help


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