This is now what my display looks like with a spline:
This is what it looks like when I turn GPU tesselation off…
Hmmmm… 
Can you send me the curve Mitch?
Not exactly the same one, but here ya go…
Curve_for_Steve.3dm (325.8 KB)
With GPU Tessellation on:
GPU-T Off:
Video card specs - NVidia 980 Ti with latest and greatest drivers (390.77)
Edit: actually I lied, it’s 388.13, I thought I had updated this machine the other day. I can install the 390.77 and see if it makes a difference…
V6 SR2 RC (6.2.18051.9541, 20-02-18)
–Mitch
Thanks, I can repeat the bug. This doesn’t have anything to do with your specific card, it’s the algorithm I use to chop up the curve into line segments. I’ll see what can be done to improve this case.
OK, thanks Steve. I did a clean install of the 390.77 drivers to check anyway and at first I thought, yay! that fixed it - but unfortunately I had quit Rhino with GPU-T off… When I turned it back on, the choppiness came right back… 
Hope you can do something with it…
Cheers, --Mitch