@Midphase - AMD openGl drivers are full of bugs and it's best to have specific combinations of hardware and drivers tested. i.e. with a AMD7950 OGL viewport selections where unusable a mere 3-4 years ago.

I was under the impression AMD uses OpenCL and that those were pretty good. I dunno, find a buddy with an iMac Pro and ask him/her to install Houdini Apprentice on it to see how it runs.

I think it the Apple openCL inplementation.

to be clear MacOS OpenGL is the issue here. AMD OpenCL is perfectly fine afaik. e.g. the Vega in the iMacPro already has a bug that delays viewport de/spliting so that rules out Vega cards for the moment.