G-Sync above 240 Hz - Why use V-Sync?

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.
kotuster
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G-Sync above 240 Hz - Why use V-Sync?

Post by kotuster » 08 Jan 2020, 08:41

I've got a 240 Hz Monitor and the games I like to play have varying frame rates that can drop as low as 100 but are mostly above 240. I'd like to know the right combination of settings that result in the least motion blur/input delay.

I've seen the interesting test's blur busters did on G-Sync + V-Sync. I don't really get why I'd want to turn on V-Sync in the fist place though. So far I have seen literally 0 screen tearing (mb I missed it, but it's minor either way) with only G-Sync enabled. Now if I leave G-Sync on and V-Sync off, is there still a reason I would want to cap my FPS to 238? That seems to be the one comparison that is missing in all the tests :D

I guess whenever my FPS go above 240 I'll get slightly lower input lag in that non-capped scenario, right? Will that result in more screen tearing every time the FPS go above 240, too, since G-Sync is turned off? I guess I won't need NULL or anything similar either way, probably just G-Sync and the 238 cap or no cap.

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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by Chief Blur Buster » 08 Jan 2020, 12:35

Caps are not perfect. A framerate can slightly fluctuate near the cap.

One frametime may be 1/235sec and the other frametime is 1/245sec. One will slightly lag and the other won’t. That’s why the famous Blur Busters “Cap a few fps below VRR max Hz” advice is given in jorim’s GSYNC 101 here at Blur Busters.

There is latency gradient differences, e.g. different top=center=bottom whenever it transitions between GSYNC and VSYNC OFF. It’s minimized at 240Hz.

If you use GSYNC + VSYNC ON, having NULL can potentially minimize lag differential between GSYNC and VSYNC ON for those rare framerate spikes that occasionally briefly exceeds an imperfect cap. Basically it’s a safety net, “just in case”.

The bigger you cap below Hz (e,g, 5fps below, like 235fps), the less often a brief exceed-240fps situation happens with an imperfect frame rate cap.
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jorimt
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by jorimt » 08 Jan 2020, 12:37

kotuster wrote:
08 Jan 2020, 08:41
I've seen the interesting test's blur busters did on G-Sync + V-Sync. I don't really get why I'd want to turn on V-Sync in the fist place though. So far I have seen literally 0 screen tearing (mb I missed it, but it's minor either way) with only G-Sync enabled.
Regarding G-SYNC + V-SYNC, read entry #2 here:
https://www.blurbusters.com/gsync/gsync ... ttings/15/

G-SYNC only works within the refresh rate; any time your FPS exceeds the refresh rate with G-SYNC on + V-SYNC off, G-SYNC isn't doing anything. That said, the higher the refresh rate, the harder it is to see tearing, as the opportunity to tear becomes less and less as the max refresh rate increases:
https://www.blurbusters.com/gsync/gsync ... ettings/6/
kotuster wrote:
08 Jan 2020, 08:41
Now if I leave G-Sync on and V-Sync off, is there still a reason I would want to cap my FPS to 238? That seems to be the one comparison that is missing in all the tests :D
Yes, to keep G-SYNC within it's range, and not revert to standalone V-SYNC OFF. This is covered here:
https://www.blurbusters.com/gsync/gsync ... ettings/2/
kotuster wrote:
08 Jan 2020, 08:41
I guess whenever my FPS go above 240 I'll get slightly lower input lag in that non-capped scenario, right? Will that result in more screen tearing every time the FPS go above 240, too, since G-Sync is turned off? I guess I won't need NULL or anything similar either way, probably just G-Sync and the 238 cap or no cap.
At 240Hz, slightly lower input lag at much higher than refresh rate framerates (see: https://www.blurbusters.com/wp-content/ ... -240Hz.png), so long as the increased framerate doesn't max out your GPU usage, at which point you'll get GPU input lag from a sustained increase in the pre-rendered frames queue.

As for more screen tearing, no, the higher the framerate above your refresh rate, the "smaller" the individual tears will be.
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kotuster
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by kotuster » 09 Jan 2020, 09:21

Very detailed answers, thanks! I'll go with the recommended G-Sync + V-Sync + 237 cap + NULL then.

I just tried testing it and set my Fortnite to 237 FPS cap (had to do it using the config file). Now my monitor (!) is displaying 240 Hz and Fortnite is displaying a max of 237 FPS in its built in counter while G-Sync is enabled. How can these numbers differ? My monitors counter is still fluctuating, so I assume G-Sync is kind of working.

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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by jorimt » 09 Jan 2020, 10:07

kotuster wrote:
09 Jan 2020, 09:21
Very detailed answers, thanks! I'll go with the recommended G-Sync + V-Sync + 237 cap + NULL then.
I actually recommend G-SYNC + V-SYNC + 237 FPS limit + Low Latency Mode "On" (not "Ultra") if you're using an FPS limiter:
https://www.blurbusters.com/gsync/gsync ... ttings/14/

I only recommend "Ultra" if you're not using an in-game limiter or RTSS, as it auto caps the FPS slightly below the refresh rate in supported games.
kotuster wrote:
09 Jan 2020, 09:21
I just tried testing it and set my Fortnite to 237 FPS cap (had to do it using the config file). Now my monitor (!) is displaying 240 Hz and Fortnite is displaying a max of 237 FPS in its built in counter while G-Sync is enabled. How can these numbers differ? My monitors counter is still fluctuating, so I assume G-Sync is kind of working.
What's your monitor model?
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kotuster
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by kotuster » 09 Jan 2020, 10:59

Yes, I set it to on, sorry.

The monitor is a Acer Nitro XF252Q. It's only G-Sync compatible. I also tested lower FPS caps now. According to the ingame FPS counter the game always respects the cap completely. According to my monitors counter the HZ number fluctuates wildly around it. If I set it to 200 it can sometimes still go up to 240 and mostly stays roughly at at 190 - 215.

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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by jorimt » 09 Jan 2020, 11:23

kotuster wrote:
09 Jan 2020, 10:59
Yes, I set it to on, sorry.
Gotcha.
kotuster wrote:
09 Jan 2020, 10:59
The monitor is a Acer Nitro XF252Q. It's only G-Sync compatible. I also tested lower FPS caps now. According to the ingame FPS counter the game always respects the cap completely. According to my monitors counter the HZ number fluctuates wildly around it. If I set it to 200 it can sometimes still go up to 240 and mostly stays roughly at at 190 - 215.
That's a tough one. It's very possible that refresh rate meter on your monitor was tuned for native FreeSync implementation, and the driver differences in the G-SYNC Compatible mode are causing inaccuracies in the readout. E.g. in G-SYNC Compatible mode, that refresh rate meter might be useless (especially since it looks like your monitor isn't on the "Official" G-SYNC Compatible list, at least as of yet).

At a 237 FPS limit, does the NVCP G-SYNC indicator (pictured below) stay on, even with the refresh rate meter fluctuations, and does your monitor have a secondary way of showing if G-SYNC is active?

Image
(jorimt: /jor-uhm-tee/)
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kotuster
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by kotuster » 09 Jan 2020, 12:04

jorimt wrote:
09 Jan 2020, 11:23
That's a tough one. It's very possible that refresh rate meter on your monitor was tuned for native FreeSync implementation, and the driver differences in the G-SYNC Compatible mode are causing inaccuracies in the readout. E.g. in G-SYNC Compatible mode, that refresh rate meter might be useless (especially since it looks like your monitor isn't on the "Official" G-SYNC Compatible list, at least as of yet).
The monitor is on the list I believe, they just have a very weird naming scheme. Some numbers just vary even though there's only one 25" model on the Acer website: https://www.acer.com/ac/en/US/content/m ... s/nitroxf2. In the list you'll find a XF250Q Cbmiiprx instead of a XF252Q Xbmiiprzx.

What's also weird is that even without V-Sync or NULL, just G-Sync, the monitor will not go above 240 Hz. So in a way the 240 FPS setting seemed to be fine, since the monitor never showed anything higher than 240. But if I set the same FPS setting to 200 the monitor goes to anything from ~180 to 240.

jorimt wrote:
09 Jan 2020, 11:23
At a 237 FPS limit, does the NVCP G-SYNC indicator (pictured below) stay on, even with the refresh rate meter fluctuations, and does your monitor have a secondary way of showing if G-SYNC is active?
I turned on the indicator in the NVCP. My monitor doesn't seem to have one. Here's a pic since it's probably hella strange to you:

Image

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jorimt
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by jorimt » 09 Jan 2020, 12:49

kotuster wrote:
09 Jan 2020, 12:04
The monitor is on the list I believe, they just have a very weird naming scheme. Some numbers just vary even though there's only one 25" model on the Acer website: https://www.acer.com/ac/en/US/content/m ... s/nitroxf2. In the list you'll find a XF250Q Cbmiiprx instead of a XF252Q Xbmiiprzx.
If that's the case, then I would simply consider your monitor's refresh rate meter to be unreliable/inaccurate in G-SYNC Compatible mode, and to disregard it.
kotuster wrote:
09 Jan 2020, 12:04
What's also weird is that even without V-Sync or NULL, just G-Sync, the monitor will not go above 240 Hz. So in a way the 240 FPS setting seemed to be fine, since the monitor never showed anything higher than 240. But if I set the same FPS setting to 200 the monitor goes to anything from ~180 to 240.
That's expected; with G-SYNC active, the refresh rate meter fluctuates only within the refresh rate, and once the framerate exceeds the refresh rate, the meter reads 240 statically (as it's no longer in the VRR range, reverting to fixed refresh rate operation) until the framerate drops within the refresh rate again.
(jorimt: /jor-uhm-tee/)
Author: Blur Busters "G-SYNC 101" Series

Display: Acer Predator XB271HU OS: Windows 10 Pro MB: ASUS ROG Maximus X Hero CPU: i7-8700k GPU: EVGA GTX 1080 Ti FTW3 RAM: 32GB G.SKILL TridentZ @3200MHz

kotuster
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Re: G-Sync above 240 Hz - Why use V-Sync?

Post by kotuster » 09 Jan 2020, 13:45

Alright, thanks! I also turned on the Nvidia FPS counter to verify it in the meantime and it shows 201 at max, mostly just 200. So it was very likely just the monitors meter that was incorrect, as you said.

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