The Myth of the Universal Frame Cap
The prevailing wisdom in PC gaming forums for the last decade has been consistent: disable V-Sync and use a frame limiter. The logic is simple and sound for a specific historical context. If you run uncapped, your GPU produces frames faster than your monitor can display them. Without V-Sync, these extra frames are not just wasted; they cause screen tearing, where parts of two different frames are visible simultaneously. A frame limiter solves this by throttling the GPU to a specific number of frames per second, typically just below the monitor's refresh rate. This prevents tearing and reduces GPU load. However, this advice ignores a critical variable: the presence of Variable Refresh Rate (VRR) technology. For players who have upgraded to G-Sync or FreeSync monitors but kept their old settings, this advice is not just unnecessary; it is actively counterproductive. It solves a problem that no longer exists while introducing new ones.
The error lies in treating all displays as if they operate with a fixed, rigid refresh cycle. They do not. VRR displays can adjust their refresh rate dynamically to match the frame rate output by the GPU. This fundamental shift changes the entire calculus of frame pacing. The "cap 3fps below refresh" rule is a heuristic designed for fixed-rate panels. It does not account for the dynamic nature of VRR. When you apply a hard cap on a VRR display, you are fighting against the very mechanism designed to make your experience smoother. You are forcing the GPU to wait for a specific time interval, whereas VRR allows the GPU to submit frames as soon as they are ready, with the display adjusting to keep up. This mismatch leads to stuttering and input lag that would not occur if you simply let the VRR system do its job.
How VRR Actually Works Under the Hood
To understand why the old advice fails, you must understand what VRR actually does. It is not a filter that removes tearing; it is a synchronization protocol that aligns the display's scanout with the GPU's frame production. In a standard fixed-rate display, the monitor refreshes at a constant frequency, say 144Hz. If your GPU produces 143.5 frames per second, the monitor will occasionally have to wait for the next frame, or display the same frame twice, or tear the image. VRR eliminates this by allowing the monitor to refresh at a variable rate, matching the GPU's output exactly. If the GPU produces a frame in 6.9 milliseconds, the monitor refreshes in 6.9 milliseconds. If it takes 7.1 milliseconds, the monitor adjusts. This eliminates tearing by design, because the display never scans out a frame while the GPU is writing a new one.
The mechanism relies on the display controller receiving a signal from the GPU indicating that a new frame is ready. The display then waits for the vertical blanking interval to pass before scanning out the new frame. This ensures that the entire frame is on the screen before the next one begins. There is no tearing because the display is always in sync with the GPU's output. The "3fps below" rule is irrelevant here because there is no fixed refresh rate to stay below. The refresh rate is whatever the GPU is producing, up to the maximum supported by the monitor. Capping the frame rate artificially restricts this dynamic range. It forces the GPU to produce frames at a fixed interval, which can cause the VRR system to engage in a "chase" mode, constantly adjusting the refresh rate to match a slightly lower, fixed target. This results in visible stuttering, particularly when the frame rate fluctuates slightly above or below the cap.
The Specific Failure of the 3FPS Rule
The "cap 3fps below refresh" rule exists for a very specific reason on non-VRR panels: to avoid the worst-case scenario of frame pacing jitter. On a 144Hz monitor, if you cap at 144, your frame times will be around 6.94ms. However, due to rounding errors and system overhead, some frames might take 7.0ms, while others take 6.9ms. This inconsistency causes visible stutter. By capping at 141 (3 below), you create a buffer. The GPU has a little more time to produce each frame, reducing the likelihood of overshooting the frame time budget. This smoothing effect is beneficial on fixed-rate panels because it ensures that every frame is displayed for exactly the same amount of time.
However, on a VRR panel, this logic is inverted. VRR is designed to handle variable frame times. It does not require uniform frame times to prevent tearing; it only requires that the display can adjust its refresh rate to match the frame time. If you cap at 141 on a 144Hz VRR monitor, you are forcing the GPU to produce frames at a rate that is not the maximum the display can handle. This means the display is running at 141Hz, not 144Hz. You are losing 3Hz of refresh rate, which translates to a slight increase in input lag and a less responsive feel. More importantly, if your GPU can produce 150 frames per second, capping at 141 forces it to throttle down, wasting potential performance. The VRR system would have happily run at 150Hz, providing a smoother experience. The cap creates a bottleneck that did not exist before.
What to Do on VRR Displays
The correct setting for a VRR display is to enable V-Sync (or VRR) in the game or driver, and to disable any frame limiter. Let the GPU produce frames as fast as it can, up to the maximum refresh rate of the monitor. The VRR system will handle the synchronization. This provides the lowest possible input lag, because frames are displayed as soon as they are ready, without waiting for a fixed interval. It also provides the highest possible frame rate, which translates to the smoothest possible motion. The only exception is if you are using a fixed-rate monitor, in which case the old advice applies. In that case, you should either enable V-Sync to prevent tearing, or use a frame limiter to cap the frame rate just below the refresh rate to smooth out frame pacing.
It is also worth noting that some games and drivers have specific settings for VRR. For example, NVIDIA's G-Sync and AMD's FreeSync have specific modes that can be enabled in the control panel. These modes ensure that the VRR system is working correctly and that the frame rate is within the supported range of the monitor. If your frame rate drops below the minimum supported by the monitor, the VRR system will disable, and you may see tearing. In this case, you might consider enabling a frame limiter to keep the frame rate within the VRR range. However, this should be a last resort, as it reduces performance. The goal is to let the VRR system work as intended, which means allowing the frame rate to vary dynamically.
When the Old Advice Still Applies
The advice to disable V-Sync and use a frame limiter is still valid for non-VRR displays. If you have a 144Hz monitor without G-Sync or FreeSync, you are stuck with a fixed refresh rate. In this case, you have two options: enable V-Sync, which prevents tearing but adds input lag, or disable V-Sync and use a frame limiter. The frame limiter allows you to reduce the input lag compared to V-Sync while still preventing tearing. The "3fps below" rule is a good starting point for this, as it provides a buffer for frame pacing jitter. However, you should experiment with different cap values to find the one that works best for your specific hardware and game. Some games may have better frame pacing with a cap of 2fps below, while others may prefer 4fps below. The key is to find the setting that provides the smoothest experience with the lowest input lag.
In summary, the advice to disable V-Sync and use a frame limiter is a relic of a pre-VRR world. It solves a problem that VRR displays do not have, while introducing new problems that VRR displays are designed to avoid. For VRR users, the correct setting is to enable VRR and disable frame limiting. For non-VRR users, the old advice still applies, but it should be tailored to your specific hardware and game. The key is to understand the mechanism behind the settings, rather than blindly following generic advice. By doing so, you can optimize your experience for your specific setup, ensuring the smoothest and most responsive gameplay possible.