OpenCL: What is it for? How do I use it?

We can choose between None, CUDA & OpenCL. What processor recognizes OpenCL?

My iMac pro says no processor is recognized by either CUDA or OpenCL

Both are mainly used to programme GPU for rendering, in the case of blender they are used by the cycles renderer. OpenCL is mostly used by AMD GPU’s , it can run on nividia but it is slow.

You also don’t use them directly, only when you render .

Apple is removing openCL at some point in the future from Mac os.

There is a thread here somewhere about Mac OS being unusable with blender because of their decision to remove both openGl and OpenCL from Mac OS in the future.

Yet, this an older OS and my gpu is AMD. I’m still missing something.

Likely upto the openCL version required by blender.