V8 wip rendering gets fast on Mac (finally!)

Rendering does not seem to work on my Intel MBP16":

I am trying to render a simple cube, but it gets stuck at Updating Lights: Importance map. When I abort the rendering (with RaytracedView as well as with Rendering) Rhino freezes…

Also: Just drawing a simple cube and switchin to Shaded View is extremely slow.

@theoutside
Edit: Raytraced Viewport works now, but this is what I get from the Render output: