I built myself a new machine with a new GPU. I tried GPU-rendering a couple benchmark files, using an untouched version of Blender. They rendered nice and fast.
But when I customize Blender by bringing in my old startup.blend and userpref.blend, then try the benchmark files again, GPU rendering is about half as fast as it should be. I checked prefs (looks good: Cycles is set to use CUDA, and my new GPU), and the Rendering tab in Properties is set to GPU Compute (although weirdly enough it’s grayed out, at least in startup.blend).
Loading factory settings and re-naming my custom startup.blend and userpref.blend files so they’re ignored at launch doesn’t seem to fix the problem. Once this particular setup of Blender has been tainted with my past settings, it stays tainted.
What gives? It’s not hard for me to re-setup stuff the way I like it, but this screws up the portability of Blender, and makes reinstalls harder in the future. And in general I’m curious about what the problem is. Anyone ever run into this?