[Thread Superseded] G-Sync 101 w/Chart (WIP)

Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.
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Re: G-Sync 101 w/Chart (WIP)

Post by jorimt » 17 Jan 2017, 11:23

hammelgammler wrote:You are totally right, I'm sorry about my comment. It was a bit confusing with your other thread where you mentioned the 1ms G-Sync penalty and to cap the FPS even lower to not have tearing. There are also some charts which may be misleading, like the 120 FPS cap on 144Hz. I was a bit confused because of that, which Information is the correct one. :/

The one thing I wanted to mention that I do had the same experience, that you need to cap your FPS much lower with V-Sync OFF. I had noticably tearing with 162 FPS, and I'm pretty sure I felt more Input Lag as well in comparison to 150 FPS. All my testing is with Overwatch and the built in limiter.

But I find it interesting that in your newest charts from this thread, that V-Sync OFF is a tiny bit faster then ON (about 1ms). So isn't it technically a bit faster? I will try it out with V-Sync ON though and write my experience with it. :)
Not a problem, I can see how my previous thread could confuse you; I was still figuring it all out. And, anyway, these comments are useful for gauging how clear or unclear a particular point of mine is. And you just brought another one up; the input latency charts.

The answer to your question is a resounding NO; 1ms is well within margin of error. If what you suggest where true, then it would mean G-Sync + v-sync off + 142 fps limit has less input latency than standalone v-sync off + 300 fps limit, which is, of course, not possible. With G-Sync + v-sync on, G-Sync + v-sync off, and v-sync off at the same fps limit, frames reach the middle level of the screen within the same time-frame, thus virtually identical input latency.

I will also try to make the margin of error clearer in my OP. If there were a 2-3 ms difference over several runs, then yes, there may (or may not) be an appreciable difference. Again though, 1ms is entirely within margin of error. At 144 Hz, for instance, if G-Sync + v-sync off + 142 fps actually had less input latency than G-Sync + v-sync on + 142 fps, you'd be seeing up to a full frame of a difference (6.9ms) or more on average.
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Re: G-Sync 101 w/Chart (WIP)

Post by MT_ » 18 Jan 2017, 16:19

Hey guys, what would be the optimal in-game cap for a 60hz gsync monitor with vsync on?

I noticed around 59 or some spikes that vsync lag kicked in.
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Re: G-Sync 101 w/Chart (WIP)

Post by jorimt » 18 Jan 2017, 16:37

MT_ wrote:Hey guys, what would be the optimal in-game cap for a 60hz gsync monitor with vsync on?

I noticed around 59 or some spikes that vsync lag kicked in.
58 fps.

57 fps if you want to be super safe, but 2 fps under the max refresh seems to do it for pretty much any refresh rate (I have 165 Hz scenario listed as 162 fps [-3 fps] suggested limit, but that may change with further input latency tests; haven't tested 163 fps yet).

After all, frametime variances/spikes tend to lower the framerate, not raise it. The 2 fps limit appears to be just enough to prevent it from reverting to v-sync behavior and delaying frame display when hitting the native refresh ceiling.

I'll be adding 60 Hz scenarios to the chart/suggested limits sometime in the future.
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Re: G-Sync 101 w/Chart (WIP)

Post by RealNC » 18 Jan 2017, 19:33

MT_ wrote:Hey guys, what would be the optimal in-game cap for a 60hz gsync monitor with vsync on?

I noticed around 59 or some spikes that vsync lag kicked in.
If you can create a 64FPS mode and cap to 60 that would be best. Dunno if it would work, but you can try it (try it with CRU.)
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Re: G-Sync 101 w/Chart (WIP)

Post by MT_ » 19 Jan 2017, 05:53

Thanks boys.

No the XB321HK wont go a single hz above 60 unfortunately :-(

I can sort of get 58ish fps with ingame fps cap but its
not super accurate. Perhaps I should toy with RTSS and put it to 59 as a 'failsafe' on top of the 57~ ingame cap?

When does Vsync actually kick in, right above 60 fps or exactly at 60? Otherwise I could put a RTSS failsafe cap at 60 for the fps spikes.
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Re: G-Sync 101 w/Chart (WIP)

Post by jorimt » 19 Jan 2017, 09:54

At 60 Hz, G-Sync starts reverting to v-sync behavior at 59 fps; G-Sync has a difficult time adjusting to those last 2 Hz (the second being the max native refresh of the display) in such a small frametime window, perhaps in part due to its polling process.

In-game caps can tend to drift a bit, especially in frametime. So yes, if you're having a difficult time with the in-game limiter, try RTSS. Stacking an external fps limit on top of an internal fps limit has no benefit that I know of.
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Re: G-Sync 101 w/Chart (WIP)

Post by MT_ » 19 Jan 2017, 16:52

jorimt wrote:At 60 Hz, G-Sync starts reverting to v-sync behavior at 59 fps; G-Sync has a difficult time adjusting to those last 2 Hz (the second being the max native refresh of the display) in such a small frametime window, perhaps in part due to its polling process.

In-game caps can tend to drift a bit, especially in frametime. So yes, if you're having a difficult time with the in-game limiter, try RTSS. Stacking an external fps limit on top of an internal fps limit has no benefit that I know of.
It would theoretically at least stop the game from engaging Vsync right? The worst thing would be the temporary extra input latency from hitting the RTSS fps cap.

Just to 'absorb' the very rarely occuring fps spikes to 59~

I wish RTSS could do decimal FPS capping.. :-(
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Re: G-Sync 101 w/Chart (WIP)

Post by jorimt » 19 Jan 2017, 17:55

I believe the latest version of RTSS can do decimal capping, you simply have to input it into the actual config file. Haven't tried it myself though.

And yes, the entire point of the fps limit is to avoid G-Sync's v-sync behavior at/above the refresh limit. Not sure if you mean stacking two fps limiters in this case; again, I don't see an advantage.

Also, in my testing, RTSS doesn't add additional input latency with G-Sync, so you shouldn't have to worry about that. And as for "spiking" to 59 fps with RTSS at a 58 fps limit, that is unlikely. Spikes usually cause lower frames, not higher frames. Anyway, you'd have to be at 59/60+ a considerable longer time for G-Sync to start acting like v-sync, which an appropriate fps limit prevents.

The only reason G-Sync begins to act like v-sync at the display's refresh rate limit is because it can no longer adjust the refresh rate to match the framerate output by the system; if you're sustaining 59+ frames for a long period, and the two frame buffers begin to over-queue, this delays frame display, which, in turn, causes the latency (at 60 Hz, double buffer latency is up to two frames delay: 16.6ms x 2 = 33.2ms additional latency).
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Re: G-Sync 101 w/Chart (WIP)

Post by RealNC » 19 Jan 2017, 18:07

MT_ wrote:I wish RTSS could do decimal FPS capping.. :-(
It does. Not through the GUI though. You need to modify the profile file. And it messes up the GUI when you do that. You need the latest RTSS for this (latest 7.x beta should work fine):

http://www.guru3d.com/files-details/rts ... nload.html

You can install it over your current version. It works fine and is compatible with the current MSI Afterburner version (if you are using that,) so you don't need a beta of that too. Just quit Afterburner, install the new RTSS, and start Afterburner again. Everything will keep working just as before.

To configure fractional caps: In the RTSS installation folder, there's a "Profiles" directory. The "Global" file (no extension) is the one for the global profile. You can edit it to:

Code: Select all

[Framerate]
Limit=599
LimitDenominator=10
This gives 59.9FPS. If you want more decimal digits, you multiply the denominator by 10. So 1 gives you no decimals (which is the default), 10 gives you one decimal, 100 gives you two (like 59.95FPS), 1000 gives you three. You don't enter the decimal point in the file though. Enter your FPS cap without a decimal ("5995" instead of "59.95".)

For a 119.977FPS cap for example, you'd write:

Code: Select all

[Framerate]
Limit=119977
LimitDenominator=1000
After the edit, you can still use the GUI to adjust the cap, but the theme was not updated to accomodate for this, so the digits might overflow into the rest of the GUI.

As a bonus, this version also supports Vulkan (so you can cap Doom 4, for example), but you need to have RTSS running BEFORE starting a Vulkan game. It can't yet hook into an already running Vulkan game.
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Re: G-Sync 101 w/Chart (WIP)

Post by MT_ » 19 Jan 2017, 19:23

jorimt wrote:I believe the latest version of RTSS can do decimal capping, you simply have to input it into the actual config file. Haven't tried it myself though.

And yes, the entire point of the fps limit is to avoid G-Sync's v-sync behavior at/above the refresh limit. Not sure if you mean stacking two fps limiters in this case; again, I don't see an advantage.

Also, in my testing, RTSS doesn't add additional input latency with G-Sync, so you shouldn't have to worry about that. And as for "spiking" to 59 fps with RTSS at a 58 fps limit, that is unlikely. Spikes usually cause lower frames, not higher frames. Anyway, you'd have to be at 59/60+ a considerable longer time for G-Sync to start acting like v-sync, which an appropriate fps limit prevents.

The only reason G-Sync begins to act like v-sync at the display's refresh rate limit is because it can no longer adjust the refresh rate to match the framerate output by the system; if you're sustaining 59+ frames for a long period, and the two frame buffers begin to over-queue, this delays frame display, which, in turn, causes the latency (at 60 Hz, double buffer latency is up to two frames delay: 16.6ms x 2 = 33.2ms additional latency).
I have already tried RTSS in combination with G-sync and surprisingly there was noticable input lag. I'm a bit surprised now as the thread start also mentions RTSS with Gsync gives no extra latency? Or is this because I have V-sync enabled as well for frametime stabilization?

Good to know on the decimal stuff though.


Another question, if someone ever tested this; Enabling Aero/Compositor in Windows 7 introduces quite some input lag. What happens though in a Windowed game with proper cap? Is it still worse than full screen exclusive? It 'feels' the same when it comes to input lag anyway...

Also how does V-sync work with G-sync in windowed mode? I guess now it uses the compositor built-in V-sync to do the frametime stabilization and such?
Last edited by MT_ on 19 Jan 2017, 19:36, edited 1 time in total.
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