Does AMD FreeSync actually removes screen tearing or just fixes other issues to make game smooth?

Question

I tried to read about AMD FreeSync on AMD and HP websites but I couldn't clear all my doubts.

Suppose there is a monitor with maximum 75Hz refresh rate. And it has FreeSync range as 48Hz-75Hz.

First, I've learned that FreeSync will work only when game FPS is below monitor's maximum refresh rate (75Hz in this case) i.e., 62 FPS. (Please correct me if I'm wrong). If it's above it, e.g., 110 FPS in the game, screen tearing issue won't solve with FreeSync. It would become useless.

So I understand that in order for FreeSync to be effective, the game FPS should fall between the FreeSync refresh rate range and it should be below monitor's maximum refresh rate.

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Now here comes the doubts. I read some posts on Reddit where many people comment that screen tearing occur when FPS is higher than refresh rate of monitor - which is correct. Others say it happens both way. Even if it is lower than refresh rate screen tearing may happen.

Some say when FPS is below refresh rate, screen tearing doesn't happen. But instead you see other issues like input lag and stuttering. And that is where FreeSync helps.

So I'm not sure how true they are when they say screen tearing doesn't happen when FPS is lower than max refresh rate of monitor. And that makes me wonder what problem does FreeSync actually fixes to improve gaming experience.

And if they are actually true, it doesn't make sense (to me) when monitor companies market the products with words like "FreeSync to fix screen tearing". I maybe wrong here but I'm not sure.

Given all that, does FreeSync actually fixes screen tearing? Or it just fixes other issues to make game experience better?

Answer 1

Screen tearing is possible below monitor's refresh rate.

Tearing happens when the GPU doesn't generate frames in sync with monitor displaying them. If the GPU finishes rendering a new frame in the middle of previous frame being sent to the monitor, half of the image displayed will come from the old frame and the rest from the new frame.

The old solution to this problem is the vertical sync. With VSync enabled, altering the image while it's being sent to the monitor is forbidden. This works well when GPU spits out more frames than the monitor can display because it effectively fixes GPU's rendering rate at monitor's refresh rate, with all frames displayed in perfect time intervals. But when the GPU can't keep up with the display, some frames will be displayed longer than others. This is perceived as stuttering.

FreeSync and G-Sync do the reverse: they make monitor's refresh intervals match GPU's render intervals, thus never sending new frames to the display in the middle of them being replaced. This fixes tearing. If the GPU keeps up with producing new frames in regular time intervals, the monitor will display them in regular intervals too, fixing the stuttering.