What is Vsync (or Vertical Sync) and how does it impact gaming?

Modern video games come with a dizzying array of graphics settings. Most of them offer better performance or better graphics quality. However, vertical sync, better known as VSync, is a bit more complicated.

By itself, VSync doesn’t affect graphics quality, but enabling it eliminates ugly screen tearing. While this might seem like a no-brainer, it can also lower your frame rate and increase input lag, both of which are the bane of competitive gaming.

Not sure how to tackle this mysterious graphics setting? Let’s see what makes VSync work.

What is VSync?

VSync is a way to synchronize the frame rate of a video game with the refresh rate of a monitor displaying it. Graphics card manufacturers developed vertical synchronization to eliminate a visual artifact known as screen tearing. This manifests as a horizontal split in the displayed frame, so that one half of the frame lags the other.

While this may appear as a tear in the space-time continuum, it’s simply your GPU that’s generating frames faster than your monitor’s maximum refresh rate. Depending on how much your GPU’s frame rate exceeds your monitor’s refresh rate, you may see two or more horizontally spliced ​​GPU frames in a single monitor refresh.

VSync eliminates screen tearing by limiting the GPU frame rate to the monitor refresh rate. However, this alone is not enough to prevent screen tearing. The setting also forces the display of GPU-rendered frames in conjunction with the monitor refresh cycle.

Preventing parts of multiple images from being visible simultaneously is key to eliminating screen tearing. And VSync achieves this by preventing the GPU from generating new frames in the middle of the monitor refresh cycle.

VSync creates more problems than it solves

While VSync is a guaranteed fix for screen tearing, it comes at the expense of performance and responsiveness. To understand why, let’s take a look at the two main features of VSync. First, it slows down the GPU frame rate to match the monitor refresh rate. Second, it also syncs the frame rate of the GPU to match the refresh rate of the monitor.

Notice how both VSync mechanisms involve slowing down the GPU output to match the refresh rate of the static monitor? This is an important detail. As the monitor refreshes at specific intervals, a GPU generates frames at a rate inversely proportional to the complexity of the game scene being rendered.

Forcing the GPU to synchronize its frame rate with the refresh rate of the monitor prevents it from relaying the most recent frame to the monitor. Gamers describe this as input lag, which is perceived as content being displayed on the monitor lagging behind their actual controller inputs. This input lag is especially pronounced in fast-paced FPS games, where the reticle lags noticeably behind your actual mouse inputs.

As if lag wasn’t bad enough, VSync can even reduce overall GPU performance by drastically reducing the frame rate. This is associated with its tendency to throttle the GPU frame rate to monitor the refresh rate. While this is fine when your GPU’s frame rate is higher than the monitor’s refresh rate, you run into issues when the frame rate drops below the refresh rate threshold.

For example, a complicated scene that forces the maximum GPU frame rate to 59 fps will not display at 59 fps on a monitor with a 60 Hz refresh rate. The required 16.67 millisecond sync interval by VSync for a 60Hz monitor will force the actual displayed frame rate to drop from 59 fps to 45 fps.

To make matters worse, GPU performance (and therefore frame rate) varies wildly during a video game. In such cases, VSync causes some images to stay on the screen longer than others. This is perceived by the viewer as a stutter or inconsistent frame rate.

What are Adaptive VSync and Fast Sync?

Fortunately, the inherent problems with VSync have not been lost on AMD and NVIDIA. Both GPU manufacturers have released their own advanced VSync flavors that alleviate the aforementioned issues. These options are either available through game settings or more generally forced through the GPU driver control suite.

Adaptive VSync

Developed by NVIDIA, Adaptive VSync eliminates all nasty input lag and performance issues introduced by GPU failing to keep up with monitor refresh rate. This VSync implementation is only active as long as the GPU can meet the refresh rate requirements of the monitor. Adaptive Sync immediately disables VSync the moment it becomes untenable. This strikes a healthy balance between gaming performance and mitigating screen tearing.

Quick sync

Also developed by NVIDIA, Fast Sync adds the magic of triple buffering to Adaptive VSync. In the simplest terms, triple buffering involves the GPU rendering an extra frame. This allows it to select the later of two rendered frames to send to the monitor while waiting for the monitor refresh cycle. The idea is to reduce input lag by displaying the most recent frame, but that also requires a lot of GPU power.

Improved synchronization

Much like NVIDIA’s Adaptive VSync offerings, AMD-specific Enhanced Sync can disable VSync the moment the GPU lags the monitor’s refresh rate. Like NVIDIA’s Fast Sync, it also uses multiple buffers to reduce input lag by delivering the most recent frame to the monitor.

Go beyond VSync

We looked at how VSync eliminates screen tearing and the drawbacks of its implementation. While NVIDIA and AMD have released more sophisticated versions of VSync that mitigate these issues, there is a whole new approach to getting around these issues with G-Sync and FreeSync technologies.

However, this requires compatible monitors, cables, and graphics cards. For those without the fancy hardware, enabling or disabling VSync is a matter of deciding where your priorities lie. VSync works well if your GPU is powerful enough to match the monitor’s refresh rate. However, it’s better to skip it if you’re not a fan of input lag.

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