While waiting for the GSYNC article Part #2 to arrive, an interesting question was asked in Blur Busters Forums about area-dependant input lag during VSYNC OFF.
It’s been long known that there can be different input lag for the top edge of the screen than the bottom edge of the screen. However, this behaves very differently with VSYNC OFF due to the mid-refresh framebuffer changes (tearing).
Here is an educational diagram of input lag of a screen refresh, during VSYNC OFF:
