Eli5 : what is vrr ‘ variable refresh rate’ and why is it useful?
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Computer monitors traditionally run at a constant refresh rate. That is, the image coming from the PC/graphics card is sent at a consistent rate over the cable. 60 Hz is most common. Even if the image isn’t changing, a new copy is sent 60 times a second regardless, with even spacing between frames. But for smoother experiences, higher refresh rates like 120 Hz are preferable, maybe even higher. A gaming monitor almost certainly does 120 Hz, and we’ll assume it can and that it does.
Note that the image is being sent over the cable over time. You can’t send a whole image instantly. It takes a few milliseconds. At 120 Hz, one frame is about 8.3 milliseconds, so the image has to be sent within that amount of time. Higher refresh rates will reduce the number of milliseconds.
However, video games require a varying amount of time to prepare an image. The CPU and GPU are doing a lot of work. If the next image isn’t ready before the graphics card starts re-sending the old frame then, you have two options: wait for the current frame to finish being sent to the monitor and then have this one sent, or splice the frame in, resulting in the monitor drawing half the old image (top half) and half the new image (bottom half). This effect is called “tearing”, since you can see a seam on screen where the two images got spliced in. Waiting for the monitor to be ready is often called the “vsync” option in video game graphics settings.
“Vsync” is the game waiting on the monitor to be ready. But Variable Refresh Rate is the other way around: the monitor waits for the game. The graphics card stops sending frames to the monitor and it just holds the current image on screen. When the frame is ready, the graphics card resumes transmission, and the next frame shows up whenever that is. There’s still a maximum rate – 120 Hz in our little example. But the amount of time between frames is no longer locked at 8.3 milliseconds, being allowed to be whatever it needs to for the game to draw the next frame. No more tearing, and no delivery delays.
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