Gadgetory

welcome back to hardware on box today we're answering one of the most frequently asked questions we see about PC gaming how many frames per second do you need should you be running at the same frame rate as your Manos maximum refresh rate say 60 FPS on a 60 Hertz monitor or is there a benefit to running games at a much higher frame rate than your monitor can display like say 500 FPS to answer this question we have to talk a bit about how GPU and display work together to send frames into your eyeballs and how technologies like vsync function but the bottom line is running games and extremely high frame rates well above your monitors refresh rate will lead to a more responsive game experience with lower perceived input latency that's instead of the question for those that don't want to wait until the end now let's talk about why this is the case so let's assume that we have a monitor with a fixed refresh rate of 60 Hertz in other words the monitor is updating its display every one sixtieth of a second or every sixteen point seven milliseconds when running a game there is no guarantee that the GPU is able to render every frame in exactly sixteen point seven milliseconds of time sometimes it might take twenty milliseconds sometimes it might take fifteen milliseconds sometimes it might take eight milliseconds that's the very nature of rendering a game on a GPU with this varying render rate there is a choice of how each rendered frame is passed to the monitor it can pass the new frame to the display as soon as it is completely rendered commonly known as running the game with vsync or vertical sync off or it can wait until the display is ready to refresh before sending the new frame that's a technique known as vsync on using the first method vsync off causes tearing this is because a display cannot update its entire in äj-- instantaneously instead it updates line by a line usually from the top of the display to the bottom and during this process a new frame may become ready from the GPU and as we're not using vsync the frame is sent to the display immediately the result is that midway through a refresh the monitor is receiving new data and updates the remainder of the lines on the display with this new data you're then left with an image the top half of the screen is from the previous frame and the bottom half is from the new freshly available frame depending on their content being displayed this split between new and old frames in the 1 refresh presents itself as a tear or visible line between the old and new frames usually it's most noticeable in fast-moving scenes where there is a large difference between one frame and the next while leasing off it does lead to tearing it has the advantage of sending a frame to the display as soon as it is finished being rendered for low latency between the GPU and the display so keep that in mind for later the alternate way to display an image is with vsync on here instead of the GPU sending its new frame to the display immediately it shuffles each rendered frame into a buffer the first buffer is used to store the frame being worked on currently and the second buffer is used to store the frame the display is currently showing at no point during the refresh is the second buffer updated so the display only shows data from one fully rendered frame and as a result you don't get tearing from an update midway through the refresh the only point at which the second buffer is updated is between the refreshes to ensure that happens the GPU Waits after it completes rendering a frame until the display is about to refresh it then shuffles the buffers begins rendering a new frame and the process repeats there are two problems with vsync firstly if your GPU rendering is too slow to keep up with the display to refresh rate say it's only capable of rendering at 40 fps for a 60 Hertz display then the GPU won't render a full frame in time to meet the start of the displays refresh so a frame is repeated and this causes stuttering as some frames are displayed only once while others are displayed twice the second problem occurs when your GPU is very fast and is easily able to render a frame within the refresh rate interval let's say it can render at 200 FPS producing a new frame every 5 milliseconds except you are using a 60 Hertz display with a 16 point seven millisecond refresh window with vsync on your GPU will complete the next frame to be displayed in 5 milliseconds then it will wait for 11.7 milliseconds before sending the frame to the second buffer to be displayed on the monitor and starting on the next this is why we vsync on the highest frame rate you'll get matches the refresh rate of the monitor as the GPU is essentially locked into rendering no faster than the refresh rate now it's at this point that there's often a lot of confusion I hear things like locking the GPU to my monitors refresh using vsync is great because if it renders faster than the refresh rate those frames are wasted because the monitor can't show them and all they get is tearing and a lot of other people point to power savings from using V sync your GPU doesn't need to work as hard there's no benefit to running at frame rates higher than the monitors refresh rate so you can run at a loc'd fps and save some power I can see why people would come to this conclusion and there's some bits of truth there but it's not accurate in general and the reason for this is that you're not factoring in the time at which inputs are processed and how long it takes for those inputs to materialize on the display to explain why this is the case let's go back and look at the vsync on diagram but overlay the diagram with the input from your mouse and keyboard which is typically gathered every one millisecond let's also use the same example where we have a GPU capable of rendering at 200 FPS with the 60 Hertz display with a vsync and a simple buffer system in this simplified explanation the GPU begins rendering a frame corresponding to your mouse input as soon as it receives that input at time zero it then takes five milliseconds to render the frame and awaits a further eleven point seven milliseconds before sending it to the display buffer the display then take some time to receive the frame to be rendered and physically update the display line-by-line with this information even in the best-case scenario we're looking at a delay of at least sixteen point seven milliseconds between your input to the game and when the display can actually begin showing you the results of that input to you when factoring in display input lag CPU processing time and so forth the latency between input and display refresh could be easily more than 50 milliseconds now let's look at the fee sink off diagram the GPU continuously renders regardless of when the display is refreshing taking five milliseconds to turn your input into a complete frame the display can then begin displaying that new frame immediately albeit it might be only part of that frame the result is the latency between your input to the game and when the display can begins showing you the results of that input reduces from sixteen point seven milliseconds to around just five milliseconds and there won't be any additional buffers in real-world implementations it's as fast as that plus your monitors input lag and that's where you get the advantage in this example running at 200 FPS with vsync off on a sixty Hertz monitor reduces input latency to five milliseconds where with vsync on that latency is at least sixteen point seven milliseconds if not more even though the display is not able to show all 200 frames per second in its entirety what the display does show every one sixtieth of a second is produced from an input much closer in time to that frame this phenomenon of course also applies with high refresh monitors at 144 Hertz for example you will be able to see many more frames each second so you'll get a smoother and more responsive experience overall but running at 200 FPS with vsync off rather than 144 FPS with vsync on will still give you a difference between 5 milliseconds and upwards of 7 milliseconds of input latency now when we're talking about millisecond differences you're probably wondering if you can actually notice this difference in games depending on the game you're playing the difference can be anything from very noticeable to no difference whatsoever a fast-paced game like csgo running at 400 fps on a 60 Hertz monitor will produce input latency at best around 2.5 milliseconds and that will feel significantly more responsive to your mouse movements than if you are running the same game at 60fps with 16.7 milliseconds of latency or more in both cases the displays only shown you a new frame 60 times a second so it won't feel as smooth as on a 144 or 240 Hertz display but the difference in input latency is enormous running at 400 FPS allows you to get your inputs to the display nearly seven times faster if not more compared to running at just 60 fps it's hard to convey the difference on camera but if you try it out for yourself you're bound to feel the difference in responsiveness and I haven't just pulled this explanation out of nowhere in fact NVIDIA knows the limitations of vsync in terms of input latency which is why they provide an alternative called fasiq this display synchronization technique is like a combination of vsync on and facing off producing the best of both worlds fast sync works by introducing additional buffer into the vsync on pipeline called the last rendered buffer this allows the GPU to continue rendering new frames into the back buffer transitioning into the last rendered buffer when complete then on a display refresh the last rendered buffer is pushed to the front buffer that the display accesses the advantage this creates is the GPU no longer waits after completing a frame for the display refresh to occur like is the case with vsync on instead the GPU keeps rendering frames so that when the display goes to access a frame at the beginning of the Refresh period that frame has been rendered more closely to the refresh window this reduces input latency however unlike with vsync off fast sync delivers a completed frame to the display at the beginning of each refresh rather than simply pushing the frame to the display immediately and it's this technique that eliminates tearing fast sync is only functional when their frame rate is higher than the displays refresh rate but it does succeed in providing more responsive game experience without tearing and of course Andy has an equivalent called enhance sync so all of this has hopefully explain why running a game above your monitors maximum refresh rate does deliver a more responsive game experience and while the ability to run games at higher frame rates is always an advantage even if it might appear that your monitor can't take advantage of it the final thing I want to say is this in this video I haven't talked about adaptive sync technologies like g-sync or free sync and that's because I've been mostly talking about running games above the maximum refresh where adaptive sync does not apply there's a lot of different syncing methods out there but adaptive sync is very different to vsync and fast sync that we've been talking about and at least for this discussion it isn't really relevant that's it for this one hopefully I won't need to answer any further questions about this in a Q&A videos because we've been getting questions on this for months if you do like what we do consider supporting us on patreon to get access to our exclusive discord channel and I'll catch you in the next one you