55.6 frames per second

[TerryRitchie]

Yes, I get 60.0 fps, but the animation is still not smooth.

The X still jumps and stutters if I track it across the screen.

If I use persistence of vision and stare in one spot, entire frames are missed:

looks kind of like this with gaps:
XXXXXX XXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXXXXX

Smooth as butter on my system, no stutters at all.