Dual Monitor Refresh Setup vs Input Lag

[jacus]

Hey, been watchin for some time - decided finally to register after purchasing my 2nd monitor, which gonna be my main now.

My decision went for XN253QX, after using XB271Hbmiprz for almost 2 years, and beein pretty happy with it, yet I've decided to throw myself in to competetive Apex Legends, and since lowest input lag is best I have few questions.

- I'm planning to stream and use both of these monitors at the same time, will I gain any extra input lag on main 253qx if I'll have both of them in g sync mode, or should I keep g-sync only on 253 and let 271 work on vsync?
- How about refresh rate on 2nd one? Does it really matter if I'll leave it at 165/170 or it's safer to stay around 60's 120's?
- Can I somehow measure input lag by myself at home without any specialistic equipment?

There is also one more thing that keeps confusing a little - currently I'm running on 1070 gtx, within a month I'll be upgrading towards 2080 super or 2080ti - the only one possible way to achieve stable 200fps~~ would be rocking 4:3 resolution and stretching it out - question is : does it affect any input lag?

We are talking about G sync On + Scaling on GPU with Full Screen Mode -

If there is thread that suits my problem, I'd be glad receiving link for it

Regards,

Jacus

[Chief Blur Buster]

- I'm planning to stream and use both of these monitors at the same time, will I gain any extra input lag on main 253qx if I'll have both of them in g sync mode, or should I keep g-sync only on 253 and let 271 work on vsync?

Focus on gaming on your primary.

- How about refresh rate on 2nd one? Does it really matter if I'll leave it at 165/170 or it's safer to stay around 60's 120's?

The biggest problem with discordant-Hz multimonitor setup is that if action is occuring on both monitors, it can lag the other monitor down in Windows.

The Windows compositor can only key to a single Hz. Best to keep content on 2nd monitor static unless your primary is running full screen exclusive (FSE). It is best to avoid windowed mode or borderless windowed mode, then it should be OK. That's the key, FSE+primary for your lag-critical content.

There is also one more thing that keeps confusing a little - currently I'm running on 1070 gtx, within a month I'll be upgrading towards 2080 super or 2080ti - the only one possible way to achieve stable 200fps~~ would be rocking 4:3 resolution and stretching it out - question is : does it affect any input lag?

On modern setups involving those GPUs, the overhead of GPU scaling on those GPUs are sub-millisecond, so you should be OK. The lag of GPU scaling is not meaningful these days anymore, and is a predictable constant (low) unlike monitor scaling.

[jacus]

- I'm planning to stream and use both of these monitors at the same time, will I gain any extra input lag on main 253qx if I'll have both of them in g sync mode, or should I keep g-sync only on 253 and let 271 work on vsync?

Focus on gaming on your primary.

- How about refresh rate on 2nd one? Does it really matter if I'll leave it at 165/170 or it's safer to stay around 60's 120's?

The biggest problem with discordant-Hz multimonitor setup is that if action is occuring on both monitors, it can lag the other monitor down in Windows.

The Windows compositor can only key to a single Hz. Best to keep content on 2nd monitor static unless your primary is running full screen exclusive (FSE). It is best to avoid windowed mode or borderless windowed mode, then it should be OK. That's the key, FSE+primary for your lag-critical content.

There is also one more thing that keeps confusing a little - currently I'm running on 1070 gtx, within a month I'll be upgrading towards 2080 super or 2080ti - the only one possible way to achieve stable 200fps~~ would be rocking 4:3 resolution and stretching it out - question is : does it affect any input lag?

On modern setups involving those GPUs, the overhead of GPU scaling on those GPUs are sub-millisecond, so you should be OK. The lag of GPU scaling is not meaningful these days anymore, and is a predictable constant (low) unlike monitor scaling.

So correct me if I'm wrong - If I'm running Apex on main screen in fullscreen mode, I can still have let's say obs + twitch chat on 2nd one? And the problems only will matter if I'll be trying to be in window full screen/windowed on my main one right? It's confusing since FSE seems to be sometimes named wrongly nowadays... to be correct - FSE is the fullscreen one which focus your game on one display and won't let you easly alt tab between screens/other application as the windowed full screen - right?

[Chief Blur Buster]

So correct me if I'm wrong - If I'm running Apex on main screen in fullscreen mode, I can still have let's say obs + twitch chat on 2nd one? And the problems only will matter if I'll be trying to be in window full screen/windowed on my main one right? It's confusing since FSE seems to be sometimes named wrongly nowadays... to be correct - FSE is the fullscreen one which focus your game on one display and won't let you easly alt tab between screens/other application as the windowed full screen - right?

Yes, generally.

The single-Hz windows compositor is what you want to avoid (adds stutter/lag).

Stay FSE on the primary when you need to do discordant-Hz multimonitor.

[ko4]

I have a 144Hz/75Hz monitor setup
I do a lot of peripheral latency testing and sometimes I get an unexplainable 5-7ms of extra lag when the system has been on for a while with both monitors connected. After I unplug the second monitor and do a restart it goes back to normal
and this is even with the game in exclusive fullscreen confirmed with presentmon