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What is G Sync doing to fps?

Discussion in 'Videocards - NVIDIA GeForce' started by eyemack, Dec 9, 2018.

  1. eyemack

    eyemack Member

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    When playing any game, this is what happens with me.
    1) G Sync set to full screen only in nVidia Control Panel (Vsync off, obviously) - 100+ fps in both full screen and windowed modes. Screen tearing in full screen, but none in windowed.
    2) G Sync set to full screen and windowed mode - 100+ fps in full screen but with screen tearing, and windowed mode restricted to 60 fps.
    So, it would seem that I always get screen tearing in full screen, and have to resort to no G Sync in windowed mode with G Sync (apparently) off.
    What is going on?
    Thanks.
     
  2. anxious_f0x

    anxious_f0x Ancient Guru

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    Basically, G-Sync only works up to your monitors refresh rate then it disengages and you get screen tearing above your monitors refresh rate, if you leave V-Sync on any fps below your refresh rate will be G-Sync'd, but if you hit your monitors refresh rate V-Sync engages and limits your fps and adds input lag.

    The usual thing to do is leave it in full screen, engage V-Sync in control panel and cap your fps -2 below your monitors refresh rate to ensure G-Sync is engaged at all times.

    For example my monitor is 100Hz, so I cap my fps to 98 and leave V-Sync on, with it setup like this G-Sync is engaged at all times.

    You can leave V-Sync off if you prefer but I've had problems with G-Sync not working at all even with an fps cap when V-Sync is off in some games.

    Hope that helps.
     
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  3. Dragam1337

    Dragam1337 Maha Guru

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    List what hardware you have...
     
  4. eyemack

    eyemack Member

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    Thanks guys, however, I remain totally confused. Why do I get tearing in full screen above 60fps with vsync off, but not in (borderless) windowed mode? I can get any frame rate in windowed without any tearing at all. Secondly, why is windowed mode restricted to 60 fps when G Sync is set to full and windowed?

    My hardware is:
    Intel i7 8700 4.8GHz · Palit RTX 2080 Ti OC Gaming Pro · ASUS ROG STRIX Z370-F · Acer 32" XB321HK · Samsung 970 500Gb M.2 NVMe · Samsung 850 Evo 500Gb · 2Tb HDD · 32Gb Corsair Vengance 3000MHz DDR4 · Windows 10 · HOTAS Warthog · TM Pedals · HTC Vive Pro
     

  5. Dragam1337

    Dragam1337 Maha Guru

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    Your issue is quite simple - your monitor does not support g-sync above 60 hz.

    Download rivatuner and limit fps to 58, and force v-sync on in global settings in NVCP.
     
  6. eyemack

    eyemack Member

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    Sorry, but it doesn't seem simple to me. Forget Gsync for the moment. Going back to my first question, why can I get tear-free fps much greater than 60 when running in borderless windowed mode, yet full screen mode tears?
    Secondly, why does borderless windowed mode go from unlimited frames when Gsync is set to full only, to being restricted to 60 fps when set to full and windowed?
    Thirdly, I thought that restricting fps to 58 was to ensure that Gsync was always kicking in, and hence there is no need for Vsync.
     
  7. Dragam1337

    Dragam1337 Maha Guru

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    No offense, but i doubt that you are not getting any tears in windowed mode when g-sync is set to fullscreen only... you might just not notice them while in windowed mode.

    There are a ton of issues connected to g-sync in windowed mode, and everyone recommends that you only run it in fullscreen mode.

    Theoretically that is correct, however i find that even when using framelimiters, frametimes will sometimes bounce out of scope, making it stutter a bit... forcing v-sync on in the global profile completely eliminates this issue for me, while having g-sync on, and limiting the framerate.

    But if you want to run at 100+ fps, why did you buy a 60 hz g-sync monitor? Seems a bit... yeah...
     
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  8. eyemack

    eyemack Member

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    Thanks again. I can assure you that there is no tearing at very high rates in full screen windowed mode when gsync is set to full only. It is very easy to test. One of my main games is DCS - which is why I have spent so much money on kit over the last year! - and it is VERY demanding depending on settings.
    I don't know if you use that software, but the easiest way to see this is to have vsync off (obviously) and gsync set to full only, then run the Instant Action Spitfire take off or cold start missions. Using TrackIR, just turn your head left and right in the cockpit and with large fps, it is easy to see the tearing on the cockpit structure. Do alt-enter, and the tearing goes away. Yes, the fps remains very high 100+ in 4K on my system.
    This is what I don't understand. Will this show in a video if I post one here?
    Am I correct in saying that if the GPU is always pumping out 60 fps - never dropping below - then Gsync is never invoked? If that is the case, then on fps limited high end systems, it seems like a waste of money.
     
  9. Dragam1337

    Dragam1337 Maha Guru

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    I don't have that software, but if you do indeed get tearless frames above 60 in windowed mode, i am not aware of how that could be, as no tech i am aware of can achieve that on a 60 hz monitor.

    That is correct - if you always run 60 fps, then g-sync will disengange, and either v-sync will engange (if you have it enabled) or it will run uncontrolled, framelimited at 60 or not.
    To make sure you engange g-sync on that monitor, you want to cap the fps at 58 or 57, either with an ingame framelimiter, or with rivatuner. Ingame framelimiting gives the least input lag, but limiting framerate in rivatuner gives more stabile frametimes, meaning it feels smoother.

    I have the exact same monitor btw, and i find that the performance with it is the best with gsync set to fullscreen only, v-sync forced on in global profile, and rivatuner limiting to 58 fps.
    I find that it is a great investment if you use it right - if your pc can handle more than the 58, just use downsampling and get prettier graphics ;)
     
  10. eyemack

    eyemack Member

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    I've uploaded a short video to try and show you 100+ with no tearing. It's not great, but hopefully you'll see what I mean. This is borderless windowed mode with gsync set to full only. I will try and do one showing how bad the tearing is when it is run in full screen with the same settings.
    http://igmack.co.uk/dcs_vid.mp4
    Hopefully you can see the fps in the top left corner from EVGA Precision showing 100+.
     

  11. BuildeR2

    BuildeR2 Ancient Guru

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    Wouldn't you end up in this situation because a borderless window has DWM triple buffer V sync applied?
     
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  12. Dragam1337

    Dragam1337 Maha Guru

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    But wouldn't that still cap the fps at the monitors refresh rate ?
     
  13. BuildeR2

    BuildeR2 Ancient Guru

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    Perhaps. Good point. OP does say in his "2" section that windowed is limited to 60FPS, his monitors refresh rate. I don't have G-sync and I always try to play in fullscreen, but the one game I had to play in borderless window (Divinity : Original Sin) wasn't capped to my refresh and didn't tear either. Could have been a one off anomaly that I stumbled upon, maybe not helpful here.

    @OP, does enabling both V and G sync not work correctly in fullscreen? As in, no tearing within the G sync range of your monitor?
     
  14. RealNC

    RealNC Ancient Guru

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    In Windowed mode you get vsync from the Window Manager. That's why there's no tearing.

    With g-sync fullscreen, if you set vsync OFF, you will get tearing if the monitor does not have a high enough refresh rate to match the game's FPS. If the game runs at 150FPS, but the monitor can't do 150Hz, you will of course get tearing. In fact, you will get tearing at about 2 to 3 FPS near the monitor's maximum Hz. On a 144Hz display, full tearing will start to happen at about 142FPS.

    You can also get tearing at lower FPS if the game has uneven frame pacing.

    Long story short, the best way to use g-sync is to limit your FPS to 3 below the refresh rate of the monitor. Make sure to:

    1. Use the highest refresh rate the monitor supports in games. (Set "Highest available" in the "Preferred refresh rate" option in the nvidia panel's 3D Settings section.)

    2. Use the game's FPS limiter, or RTSS if the game doesn't have one, to cap your FPS to 3FPS below the maximum refresh rate. On a 144Hz display, you need to cap to 141FPS.

    3. Disable vsync in the in-game settings. Set vsync to ON in the nvidia panel. (You can also set it to OFF if you want, and only set it to ON for games where you can still see some tearing.)

    Note that when you cap your FPS to 3 below the refresh rate, setting vsync ON in the nvidia panel will not increase input lag. It will protect you from temporary tearing, but there is no input lag penalty.

    For much more detailed information about how to best use gsync and how much input lag there is, you can read this article. It has 14 pages will lots of information and testing:

    https://www.blurbusters.com/gsync/gsync101
     
  15. tsunami231

    tsunami231 Ancient Guru

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    No DWM version of vsync is not restricted to the monitor hz and as far as i am aware in windows 10 you cant disable DWM "vsync" like in windows 7 ? all windows programs/games have a form of vsync enabled due to DWM, which why it dont tear the fact there is no FPS restriction associated with the monitors hz is why alot people think there not using vsync in fullscreen windowed, it is there and it is on and it does have input lag associated with it but it is not as noticeable as vsync in fullscreen exclusive apparently

    Setting Vsync on in NVCP has no effect on windowed programs/games only fullscreen *exclusive* but at same time IF you have game that has in game vsync options and options for fullscreen exclusive and fullscreen windowed, setting said games in game vsync on will limit the fullscreen windowed to monitor hz

    Atlest this how i seen Windows fullscreen work it has no tearing cause of DWM version of vsync and it not limited to monitor hz unless the game it self has vsync options that is enabled.
     

  16. Cyberdyne

    Cyberdyne Ancient Guru

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    Something that really frustrated me is that some months ago NVidia changed Gsync's behavior to actually HAVE tearing when it's on without Vsync on. In the past Vsync could be off and as long as your frame rate was below your refresh rate you were golden. Now, tearing can be seen in every game I tried. It seems to try and push the tear lines to the top and/or bottom of the screen to hide it. I think this was done because AMD's drivers do a similar thing with Freesync, and some people prefer it (for some reason).

    With Vsync on, its just like it was in the past though, so it's not a deal breaker. But it did really confuse me when the change happened.

    The only downfall to this is, it's hard to test if Gsync breaks. What I mean by that is, sometimes Gsync does not engage properly and you might need to reapply Gsync in the driver (Which usually even works just by tabing out while you're playing) or switch around the resolution to get it going. In the past it was easy to tell if it broke, you would clearly see tearing because you had Vsync off. But now you need to pay really close attention to input lag to know if Gsync broke. (just to clarify, usually Gsync breaks in games with bad fullscreen/windowed implementation, ESPECIALLY Unity games).
     
  17. Astyanax

    Astyanax Ancient Guru

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    a mistake many make is calling the buffering that dwm uses "Triple buffering"

    It isn't, its a double buffered presentation mode which isn't explicitly tied to the swap interval. this happens to be why multimonitor setups with mixed refresh rates suffer when content is active on the lower hertz screen.
     
  18. eyemack

    eyemack Member

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    Thanks a lot, guys. I don't fully understand everything you've been saying, but I have taken a lot in!
    As far as I can see, especially since I bought a 2080 Ti a few days ago, that Gsync has limited use for me as even at highest settings in 4K, I am hitting the (frame limited) 58 fps barrier. If I am wrong, please correct me.
    One thing that still bothers me though, if borderless windowed mode can do 100+ fps without tearing, then why not use it? What is the actual benefit of going exclusive full screen?
    In answer to a question several posts ago, i.e. why did I buy a Gsync monitor if I wanted to run games at 100+ fps, well, the reason was that I couldn't see a 4K 30"+ 144Hz model around at the time. If anyone can point me to one, I would appreciate it.
     
  19. RealNC

    RealNC Ancient Guru

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    Stuttering.

    Less input lag.
     
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  20. Dragam1337

    Dragam1337 Maha Guru

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    Gsync is not of limited use to you, as it is still far superior than the alternatives in terms of input lag, and frame delivery stability.

    Just do as i said - stick with g-sync at 58 fps, and then use downsampling to make your graphics even better looking - i assume that you are using 4k in the first place, because you want pretty graphics ;)

    There are currently only 2 4k 144 hz screens, but they are both 27".
     
    Last edited: Dec 10, 2018
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