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I am using GPU rendering and my CPU is really bottlenecking blender down to only 50% of max GPU performance, while blender is taking up more than 90% of my CPU usage. How can I put less strain on my CPU so it will stop bottlenecking my GPU?

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    $\begingroup$ Not all operations during render are done in the GPU, the CPU is not idle while rendering. $\endgroup$ – cegaton Aug 21 '17 at 14:12
  • $\begingroup$ What do you mean by making it 'easier' on your CPU? If you are on a laptop and the CPU is heating up too much, there are ways to reduce the CPU speed at the expense of slower performance. If you think the CPU is bottlenecking your GPU, then you want to speed up your CPU, not slowing it down. $\endgroup$ – Mike Pan Aug 22 '17 at 6:18
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Even if you are rendering on GPU that does not mean evetything runs on it.

And things like physics, BVH creation, etc has to be made via CPU still.

So if your CPU is a bottleneck that is likely to happen always.

The only thing you can do is lower the number of threads Blender uses:

Blender threads

That will release CPU power but may slow the render

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  • $\begingroup$ ok thanks, ill try it out(wonderful screenshot btw), what do threads do? $\endgroup$ – snipers500 Aug 21 '17 at 19:32
  • $\begingroup$ I found out what threads are, but I'm trying to reduce load on my CPU to make the GPU rendering go quicker $\endgroup$ – snipers500 Aug 21 '17 at 19:37
  • $\begingroup$ @marsh you don't have to use your phone to make screenshots. Simply press Ctrl F3 in blender and save the screen as a file. Real screen grabs are easier to read. $\endgroup$ – cegaton Aug 21 '17 at 21:43
  • $\begingroup$ @cegaton, I was answering from my mbl sry :') $\endgroup$ – marsh Aug 22 '17 at 0:44
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    $\begingroup$ @snipers500 You should take your time to learn about the Performance tab in Blender, it will help a lot your render times $\endgroup$ – marsh Aug 22 '17 at 0:47
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If 90% of CPU load bothers you, ie its not comfortable to work with other programs, you can set priority to the Blender by Task Manager.

Press Ctrl+Shift+Esc to launch Task Manager.

Prior Windows 10, right click on Blender process->Set Priority->Low. In the Windows 10 select details tab, and again right click on Blender process->Set Priority->Low

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  • $\begingroup$ Also, you can launch "powershell ise" with admin privileges, then paste Get-Process | where ProcessName -eq "blender" | ForEach-Object {$_.PriorityClass="Idle"} $\endgroup$ – Oleg Skripnyak Aug 21 '17 at 16:38
  • $\begingroup$ Btw, by lowering number of threads, you lower performance, because they are executed per core/processor, so in case of Intel i5, there are 4 cores, and therefore 4 concurrent threads which can do max performance. Can't reply to you directly because of reputation limits. Hope that help $\endgroup$ – Oleg Skripnyak Aug 22 '17 at 1:55

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