I just installed a 3960x a few days ago. I don't get this kind of slow down(free tier), however I did notice a 100% usage spike across all cores during tumbling.

Check all the "Octane Camera Imager" panels and be sure your settings are all matched. You might have some LUT applied on one and not another..

Has anyone tried the new 418.91 yet?

I would expect this to be a bug? it is still present in the latest 3.05.3 / 11.22 releases..

I experienced this too, especially in regards to border rendering, if I initiate a viewport preview render with border switched off then my render preview stops at the allotted number of samples.. However if I set border rendering then it overshoots the preview samples and carries on regardless. I ...