Sli and Dual monitors make me wanna rip my hair out

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richjim

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PROBLEM: It took me a while to setup SLI (fist time doing it) but I got it working. Now basically in some games like CS:GO or H1Z1, I get like 2 fps even from launch, or horrible stutter every ~5 seconds... UNTIL I unplug my 2nd monitor. Then everything runs perfectly.

STORY:
I just bought a second Nvidia GTX 970 (Asus Strix) to try SLI

I also bought a second monitor: Asus ROG Swift PG278Q 27-Inch [Yay black friday + credit cards]

So my current setup is:
Nvidia GTX 970 (Asus Strix) x2 SLI
Main mintor: Asus ROG Swift PG278Q
Side monitor: ASUS PB278Q

Both of my monitors are 1440p, 27 inches. But the Rog is 144hz Gsync, and the other is 60hz. Both are plugged into the same card, one with DP, the other with DVI.

I want to use the rog for gaming (faster) and the other for photoshop/video stuff (better looking display). I need both.

But with the issues I'm having, IDK if its due to the monitors or the SLI.

~~Stuff I've tried~~
Even games like The Witcher 3 and GTAV were stuttering before so I changed the scaling setting to be GPU on both monitors, which fixed it for those games, but now here we are with the other games having issues.

All games are in full screen mode.

Other info about my rig:
CPU: i7 6700k
Mobo: GA-Z170X
PSU: CX750M (750w corsair)
Ram: 16gb

Plz help!:(
 
Solution
Eximo
G-Sync is a monitor to GPU technology that does work with SLI through the Display Port. This lets the GPU directly control the scalar, and thus refresh rate, of the ROG monitor rather then the monitor being at a fixed refresh rate.

What you are doing is asking a set of cards to output 60Hz and 30-144Hz to two different monitors using two different connection methods. Regardless of how many cards you use for this that would seem to be the fundamental problem. Testing would be simple. Just disable SLI, or disable G-Sync, or both and see if the problem persists.

I have found that G-Sync will override some in-game settings such as frame rate limits. V-sync needs to be off in game engines for G-Sync to work as well. Though in practice...
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bailojustin

bailojustin

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Just a guess, IM pretty sure the refresh rates have to be the same, unless you have the 144 monitor plugged into the other card and have the settings in nvidia control panel to frame cap at 144hz and the opposite card capped at 60hz, Im not sure your going to be able to run full screen games utilizing both cards because its having to render 2 different refresh rates. with 2 144hz monitors I dont think it would be an issue.
 
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Eximo

Eximo

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Yeah, not sure about G-Sync + non G-sync with non matching Hz. Having one monitor communicate to the card via a G-sync module and the other via a normal monitor scalar... That just seems like you are asking for trouble.

They just added support for Windowed G-Sync mode not too long ago. I think we are still a long way from seamless support.
 
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richjim

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So basically you guys are saying its an issue with the monitors? Which is a relief if the SLI works fine.

I have thought about running the second monitor through on board graphics, but wouldnt it struggle with photoshop/premiere pro/after effects?
 
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Eximo

Eximo

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Not a problem with the monitors. You are asking a set of SLI'd video cards (wherein each card renders every other frame) to create content for one monitor that the GPU is controlling the refresh rate of and one monitor that is operating its own scalar, and running a static frequency compared to the dynamic frequency on the ROG Swift. I can't even conceive of how that would work.

If you are using Photoshop, Premiere, and After Effects then you would want to disable G-Sync and probably set both screens to 60Hz for the use of multiple monitors. I would not attempt to use both monitors simultaneously for any Full Screen type applications.
 
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richjim

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I see... so my main problem is with the gsync? I wouldn't be having issues with a single GPU?

If that's the case I'll just return my second card and wait for Pascal or soemthing.

I've read of other people using monitors with different refresh rates with not issues but they probably didnt have gsync to worry about.
 
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Eximo

Eximo

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G-Sync is a monitor to GPU technology that does work with SLI through the Display Port. This lets the GPU directly control the scalar, and thus refresh rate, of the ROG monitor rather then the monitor being at a fixed refresh rate.

What you are doing is asking a set of cards to output 60Hz and 30-144Hz to two different monitors using two different connection methods. Regardless of how many cards you use for this that would seem to be the fundamental problem. Testing would be simple. Just disable SLI, or disable G-Sync, or both and see if the problem persists.

I have found that G-Sync will override some in-game settings such as frame rate limits. V-sync needs to be off in game engines for G-Sync to work as well. Though in practice, more often then not, the game will ignore its own settings unless the engine is restarted with either G-Sync enabled or disabled.


 
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Solution
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richjim

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I see what you're saying. I have tried it with SLI off and didnt have any issues, so single GPU seems to be OK with this setup. I'll see if plugging my non-rog to the on board works for my uses, if not I'll be waiting for a single gpu upgrade.

Thanks for your help!
 
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