G-SYNC 101: G-SYNC vs. V-SYNC w/FPS Limit


So Close, Yet So Far Apart

On the subject of single, tear-free frame delivery, how does standalone double buffer V-SYNC compare to G-SYNC with the same framerate limit?

Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings
Blur Buster's G-SYNC 101: Input Latency & Optimal Settings

As the results show, but for 60Hz (remember, a “frame” of delay is relative to the refresh rate), the numbers are relatively close. So what’s so great about G-SYNC’s ability to adjust the refresh rate to the framerate, if the majority of added input latency with V-SYNC can be eliminated with a simple FPS limit? Well, as the title of this section hints, it’s not quite that cut and dry…

While it’s common knowledge that limiting the FPS below the refresh rate with V-SYNC prevents the over-queuing of frames, and thus majority of added input latency, it isn’t without its downsides.

Unlike G-SYNC, V-SYNC must attempt to time frame delivery to the fixed refresh rate of the display. If it misses a single one of these delivery windows below the maximum refresh rate, the current frame must repeat once until the next frame can be displayed, locking the framerate to half the refresh rate, causing stutter. If the framerate exceeds the maximum refresh rate, the display can’t keep up with frame output, as rendered frames over-queue in both buffers, and appearance of frames is delayed yet again, which is why an FPS limit is needed to prevent this in the first place.

When an FPS limit is set with V-SYNC, the times it can deliver frames per second is shrunk. If, for instance, the FPS limiter is set to 59 fps on a 60Hz display, instead of 60 frames being delivered per second, only 59 will be delivered, which means roughly every second a frame will repeat.

As the numbers show, while G-SYNC and V-SYNC averages are close over a period of frames, evident by the maximums, it eventually adds up, causing 1/2 to 1 frame of accumulative delay, as well as recurring stutter due to repeated frames. This is why it is recommended to set a V-SYNC FPS limit mere decimals below the refresh rate via external programs such as RTSS.

That said, an FPS limit is superior to no FPS limit with double buffer V-SYNC, so long as the framerate can be sustained above the refresh rate at all times. However, G-SYNC’s ability to adjust the refresh rate to the framerate eliminates this issue entirely, and, yet again, beats V-SYNC hands down.



1796 Comments For “G-SYNC 101”

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BlackStorm82
Member
BlackStorm82

Hello, is it true that the monitor with the GSYNC module contains GPU scaling?

And is it also true that GSYNC module monitor cannot use display scaling?

If GPU scaling is forced on the GSYNC module monitor. GPU scaling is used as “no scaling” in the NVIDIA control panel, and if the resolution and direct resolution of the game are the same, it doesn’t work anyway?

Also, is it the same story for GSYNC compatible monitors or only GSYNC module monitors?

Deus_nsf
Member
Deus_nsf

Please take a look at this, we may have a solution for the windowed mode nightmare that doesn’t require owning an adaptive sync display!!! https://steamcommunity.com/app/993090/discussions/0/3053989078739351832/?ctp=4

biggydeen
Member
biggydeen

Hi,

First I like to thank you for this awesome guide. I’m sure you helped tens of thousands of people to get the best out of their g-sync/freesync screen.

I do have a question no one else could anwser. Maybe you know what is going on with my system and if it is related to g-sync/freesync.

My current settings:

  • 144hz screen (LG 27GL850 Ultragear, G-sync compatible)
  • G-sync (fullscreen mode) on
  • V-sync on in NVCP
  • Framelimit 140 in RTSS
  • Core park on
  • Turned off vsync ingame and any buffers if they are available
  • Low latency mode is set to “on”.
  • Basically, exactly what you mention as the optimal settings. I’m not using any overlays like g-force exp. and RTSS.

    My problem:

    I’m expieriencing some kind of (micro)stuttering when my frames drop below 140. But it’s application dependent. For example:

    When i’m playing Battlefield V on the smaller snowmap (without the train) I constantly get 140 fps. This map runs butter smooth as I would expect with free-sync. Other smaller maps also run butter smooth. When playing the bigger snow map (with the train) and fps sometimes dips below 140 (like 135) i’m expierincing some kind of stuttering. It’s just not smooth like the smaller maps. Now this confuses me because it’s only dipping 5 frames or so below my FPS cap. But the difference for me is night and day. I have the same expierence on all maps in BF V where the frames drop just a bit below my limit.

    When I run the Timespy benchmark, everything is butter smooth. But i’m no where near my fps cap. In the first demo the FPS is going all over the place dipping to 60 and all the way up to 120 but everything looks butter smooth.

    When playing Sea of Thieves I have the same problem as BF 5. When FPS goes down the smoothness is gone. Eventhough FPS is above 100.

    It’s definitely not a hardware problem (unless my screen is the problem). I’ve had the same issue with completely other hardware. I already have a new cpu, gpu and ram. Same issue’s.

    To give you an idea what i’m expierencing:

    I did expierence the same thing when I was still using a 60hz screen + vsync. If FPS dropped below 60, even if it’s 1 frame, the smoothness is gone. That would be expected with a 60hz + vsync but I would not expect this with free-sync only dropping a few frames and way above 130 fps.

    The strange thing is, this does not always happen. Like the timespy example, everything is butter smooth but the FPS is not even near the fps cap. So, free-sync is working just fine.

    Do you have any idea what i’m facing here? Could it be CPU related because BF5 is very CPU heavy and basically always hits 100% cpu use ( i’m running the 5800x). But some cores are actually running 100% on the small now map (I checked) but on that map everything is butter smooth.

    wellroman
    Member
    wellroman

    Hi, I’m here for an advice and I hope I’ll get one from smart people. I bought 165hz monitor with g-sync and I want to use it but I really do care about my input delay so I want to know what option is going to be the best in my situation:

    1. 165 hz monitor + 162 in game fps lock + g-sync on + v-sync on
    2. 165 hz monitor + 162 in game fps lock + g-sync on + v-sync off
    3. 165 hz monitor + 180 in game fps lock + g-sync off + v-sync off

    So the questions are:

    • Does the v-sync even make sense with g-sync and will I get less input delay by turning v-sync on or by turning it off (while with g-sync)?

    • Should I even use g-sync? Is there a big difference in the input delay between the option 1 and option 3 in my list?

    I hope you got my questions right and will help me))

    xpnkz
    Member
    xpnkz

    Beautiful, this is like the holy grail when it comes to G-Sync information, thanks.

    I just want to ask over to be sure, since I recently switched to a Nvidia GPU with a G-Sync Compatible display and reading the comments I saw some conflicting comments too, specially since late driver updates seems to have changed a bunch of things (for example no more display selection under G-SYNC tab, but just says “Set the G-SYNC capable display as the primary display”).

    So for the best results, all I have to do in Nvidia Control Panel is:

    ● G-Sync: “ON” (Fullscreen) in the G-Sync tab and Monitor Technology set to “G-Sync” too?
    ● Vertical Synchronization: “V-Sync ON” (not Fast Sync)
    ● Low Latency Mode: “ULTRA”
    ● Max Frame Rate: “141” (my monitor is 144Hz)
    ● In game: V-Sync or related settings all OFF

    If someone can quickly glance over this and say if it’s correct, thanks!

    wpDiscuz