Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

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nursejoy
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Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by nursejoy » 02 Jun 2020, 17:05

MAYBE A NOOB QUESTION SO APOLOGIES
So I have a gaming monitor. A 24" 240hz monitor thats gsync compatible the asus xg248q. It works wonderfully playing console and PC games. I was considering adding this monitor just for web browsing and such and putting it vertically. https://www.amazon.com/BenQ-PD2500Q-256 ... B0749RC47S. But apparently this monitor is really laggy. It doesn't matter to me at all but I was wondering since it will be connected to the same GPU as my gaming monitor will it matter? The gaming monitor will also be the main display.

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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by Chief Blur Buster » 02 Jun 2020, 17:06

Yes for two reasons
(A) Windows compositor doesn't have independent compositors for separate monitors (OS induced)
(B) Screen activity in other apps can slow down the 3D of the main monitor (performance)

See viewtopic.php?f=10&t=6965

If you want to minimize this problem, use fullscreen exclusive (not borderless) for your 240Hz primary, and make sure that any browser animations have stopped (disable ads). Static pages combined with FSE games, is your best bet. Or just minimize windows until you need to show a walkthrough guide / walkthrough video or such.
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nursejoy
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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by nursejoy » 02 Jun 2020, 17:11

By minimize you mean completely remove or just make the issue less? Most games I play are exclusive fullscreen but some games or emulators just don't support it. Dumb I know.


Also yeah I do know that, I actually did a ton of research before purchasing this monitor. It was actually YOU who told me about it being low-lag 60hz and the reasoning behind it. I appreciate you! Are there other low lag 240hz monitors that you know of at the top of ur head? Want to recommend some to friends as the XG248 is sold out

senny22
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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by senny22 » 03 Jun 2020, 04:23

Chief Blur Buster wrote:
02 Jun 2020, 17:06
Yes for two reasons
(A) Windows compositor doesn't have independent compositors for separate monitors (OS induced)
(B) Screen activity in other apps can slow down the 3D of the main monitor (performance)

See viewtopic.php?f=10&t=6965

If you want to minimize this problem, use fullscreen exclusive (not borderless) for your 240Hz primary, and make sure that any browser animations have stopped (disable ads). Static pages combined with FSE games, is your best bet. Or just minimize windows until you need to show a walkthrough guide / walkthrough video or such.
Does this mean watching series on a second monitor increases input lag on my game even though I use exclusive fullscreens?

Is this true for any program that has moving images? Such as a music player like Spotify tidal where the slider is constantly moving when playing a song?

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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by Chief Blur Buster » 03 Jun 2020, 13:43

senny22 wrote:
03 Jun 2020, 04:23
Is this true for any program that has moving images? Such as a music player like Spotify tidal where the slider is constantly moving when playing a song?
Your clue will be the frametime latency (that "GPU" segment of lag chain).

Image

In an ideal situation, if the 2nd monitor is only consuming 5% of GPU, it will add only 5% extra frametime latency to the main monitor. For example, if keeping the 2nd monitor enabled reduces your frame rate by 5%, e.g. 100fps down to 95fps, your frametimes increased from 10ms to 10.5ms. Half a millisecond more latency.

To find out how much lag your 2nd monitor is increasing.
1. Get your game's framerate with 2nd monitor disconnected, no 2nd app running
2. Get your game's framerate with 2nd monitor connected, with 2nd app running (like music player)
3. Compute the frametime (1/fps)
4. Difference between frametimes is your lag penalty of running an app on that 2nd monitor.

Causes of frametime increases:
A. Memory (GPU/CPU) consumed by 2nd monitor
B. Processing (GPU/CPU) consumed by 2nd monitor

This assumes you're running in fullscreen exclusive and not subject to extra latency caused by the single-monitor-syncing Windows compositor (dwm.exe). I wish Microsoft would multithread the compositors so that each monitor had its own separate, independent compositor, for monitors getting different pixel clocks (the Pixel Clock number in a Custom Resolution Utility -- if they mismatch, the monitors won't ever be able to be in perfect sync).

If compositors are out of sync, and you use borderless windowed, your latency can sawtooth in a range of [0...refreshtime] if there are at least 1 pixel being updated on both monitors. This is because dwm.exe syncs only to one monitor. This is the far worse lag error margin with a multimonitor system. The interval of refreshes for 144Hz is 1/144sec = 6.9ms, so borderless windowed games can get erratic stutters [+ erratic lag] when stuff updates on the 2nd monitor (even a slowly animating banner ad or a notification bubble appearing).

So.... Always use fullscreen exclusive to avoid the 2nd monitor affecting the lag of the primary monitor! Then you only need to worry about frametime lag (caused by other apps slowing down your game).
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TTT
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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by TTT » 03 Jun 2020, 14:55

I was looking through my bios other day (Asus TUF Z370-Plus).

I saw an option to turn on to enable your integrated graphics in the CPU to run a second monitor.

Would this help in this situaiton?

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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by Chief Blur Buster » 03 Jun 2020, 16:50

TTT wrote:
03 Jun 2020, 14:55
I was looking through my bios other day (Asus TUF Z370-Plus).

I saw an option to turn on to enable your integrated graphics in the CPU to run a second monitor.

Would this help in this situaiton?
I do not think so, at least for the dwm.exe compositor (the major problem). GPU offload is much more minor than the dwm.exe problem
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       To support Blur Busters:
       • Official List of Best Gaming Monitors
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       • List of FreeSync Monitors
       • List of Ultrawide Monitors

nursejoy
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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by nursejoy » 05 Jun 2020, 01:02

senny22 wrote:
03 Jun 2020, 04:23
Chief Blur Buster wrote:
02 Jun 2020, 17:06
Yes for two reasons
(A) Windows compositor doesn't have independent compositors for separate monitors (OS induced)
(B) Screen activity in other apps can slow down the 3D of the main monitor (performance)

See viewtopic.php?f=10&t=6965

If you want to minimize this problem, use fullscreen exclusive (not borderless) for your 240Hz primary, and make sure that any browser animations have stopped (disable ads). Static pages combined with FSE games, is your best bet. Or just minimize windows until you need to show a walkthrough guide / walkthrough video or such.
Does this mean watching series on a second monitor increases input lag on my game even though I use exclusive fullscreens?

Is this true for any program that has moving images? Such as a music player like Spotify tidal where the slider is constantly moving when playing a song?
Will the lag vary from one monitor to another. I already have a second monitor (viewsonic vp2468) that is rated to have 9.4ms input lag (it runs at 60hz), and I'm totally satisfied with the lag when I play games on exclusive fullscreen on my main gaming monitor (Asus Vg248). Learning that a 2nd monitor adds delay if I'm either not running FSE or have it on FSE while having active applications opened on the 2nd monitor I was wondering if it would be worse if I replaced the 2nd monitor with another one thats has more input lag?

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Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by Chief Blur Buster » 05 Jun 2020, 01:08

nursejoy wrote:
05 Jun 2020, 01:02
Will the lag vary from one monitor to another. I already have a second monitor (viewsonic vp2468) that is rated to have 9.4ms input lag (it runs at 60hz), and I'm totally satisfied with the lag when I play games on exclusive fullscreen on my main gaming monitor (Asus Vg248). Learning that a 2nd monitor adds delay if I'm either not running FSE or have it on FSE while having active applications opened on the 2nd monitor I was wondering if it would be worse if I replaced the 2nd monitor with another one thats has more input lag?
Primary monitor lag is unaffected by secondary monitor lag.

The GPU has absolutely no knowledge if a monitor is laggier or not. Whatever happens to pixels after it's output of the video port, is no longer the GPU's responsibility anymore.

Multimonitor latency is simply an adder (a plus modifier) to whatever latency each monitor has, independently for each monitor.

Totally different part of latency chains being added together. This is a separate-silo situation.
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       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors

nursejoy
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Joined: 02 Jun 2020, 17:01

Re: Does using a 2nd monitor (only for web browsing) affect input lag while gaming?

Post by nursejoy » 05 Jun 2020, 01:14

So basically I can have a 2nd monitor with 100 frames of input delay connected to the same machine as my gaming monitor but my main gaming monitor will still run at its lowest lag?

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