Consistent tear-line at the bottom with Vsync OFF + VRR + below max Hz Cap

[Luviaz]

Disclaimer: I'm not trying to troubleshoot, the problem being disscussed purely for better understanding.

I have noticed in a few games which full-screen mode force a 60Hz refresh rate. VRR still working as it should with a cap of 57 FPS, but a constant, stable tear-line is rendered with Vsync OFF, as if VSync OFF + no VRR.

I'm fully aware from GSYNC 101, that this is easily fixed by simply enable VSync, and VRR + Vsync OFF do not prevent tearing, but how exactly ?

I mean technically, there is no way for a tear to occur in VRR + under max Hz cap. Let's take 57 FPS cap 60Hz VRR Vsync-Off for example. No frame could start after ~17.5ms, thats plenty of time for VRR to do the scanout ( 16.6ms ), looping for and extra ms, and scan a new frame. Maybe 3 FPS is too close and RTSS couldn't precisely cap at microseconds ?

Tearing go away when the Max HZ increased, 60FPS Vsync off VRR at 120Hz + is tear-free.