Blender not using all 128 cores

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1

I have a HP DL980 G7 box, with 64 physical cores (128 logical cores). When I render, it uses only 64 of the logical cores. I got around the issue by running 2 instances of blender, then I could get all 128 cores working at the same time.
Is there a limitation in blender for 64 cores, or it it not using hyperthreaded cores?

2

I’m not an expert but I think that you can change how many cores Blender uses. Go to the “Render” tab in the “Properties” Panel. Then in the “Performance” rollout you’ll see a “Threads” option. You can set it to “Auto-detect” to try and detect all cores or “Fixed” and enter 128. Does this work?

3

Hi, Blender is limited in mega core usage (asked developer).
There are also problems with overhead and render is slower with one instance.

Cheers, mib
EDIT: Which OS you are using?