[P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Any issues, problems or troubleshooting topics related to computer hardware and the Prepar3D client application
Nemex
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Joined: Thu Dec 18, 2014 4:40 pm

[P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby Nemex » Sat Jun 03, 2017 1:13 pm

Hi,

I have the following problem:

I run P3D v4 on a dual GTX 1080 system with 3x 1440p screens in SLI + Surround mode. It works wonderful, the SLI scaling is really good and in heavy areas i get near 100% load on both GPUs. The only problem is, that effects, like the lights from lamps, contrails or the cloud motion effect of Active Sky aren't showing on the right screen. They show up fine on the left and middle screen.

I have the screens connected as per NVIDIA requirements:

left and middle screen to GPU 1
right screen to GPU 2

I use a HB SLI bridge to connect the 2 GPUs.

So it looks like the effects somehow don't make it to the 2nd GPU?
I had this issue for a while in P3D v3 aswell, but couldn't figure out any way to fix it.

Everything besides the effects shows perfect on all 3 screens.

Cheers
Andreas

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Beau Hollis
Lockheed Martin
Posts: 1888
Joined: Wed Oct 06, 2010 3:25 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby Beau Hollis » Tue Jun 06, 2017 2:13 pm

Can you provide more specifics on your SLI settings? Our SLI integration is based on alternate frame rendering (AFR). We query the driver for info on AFR groups. I'm not sure what options are used in the case of SLI-surround.

Are you using a single 3D view, or 3 view?

If you use disable SLI and put a view on each screen, do you still see effects? (If you have standard tripple screen setup, the auto-detect view group should work pretty well for testing this.)

If you plug all monitors into the first GPU and put SLI into performance mode, do you see effects? If this works, how does performance compare?

Final note on your setup options:
- Non-SLI with 1 view stretched: This will only use one GPU.
- Non-SLI with 3 views: This will use whatever GPU each monitor is plugged into, so you still use both GPUs. Three views comes at a CPU hit, but you get less distortion if each screen has it's own projection. View groups can be used to set up the custom projections for you.
- SLI performance 1 view stretched: I think this may require monitors be plugged in to first GPU.

Thanks
Beau Hollis
Prepar3D Software Architect

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Beau Hollis
Lockheed Martin
Posts: 1888
Joined: Wed Oct 06, 2010 3:25 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby Beau Hollis » Wed Jun 07, 2017 5:55 pm

Our recommendation for now is to disable nvsurround. We were able to reproduce the issue, but it appears to be a driver issue. If you save a screenshot using the V key, all affects will show up correctly in the screenshot. If you take a screenshot via Print-Screen and paste into paint, no effects show up in the screenshot. Nvidia reports there are 2 AFR groups, but never swaps between groups. Our theory is that the driver is simply rendering the entire scene on both GPUs every frame, rather than rendering alternate frames on each GPU.

Thanks
Beau Hollis
Prepar3D Software Architect

Nemex
Posts: 12
Joined: Thu Dec 18, 2014 4:40 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby Nemex » Thu Jun 08, 2017 5:25 pm

Thank you very much for the info!

I will try the alternative methods you mentioned when I have time this weekend.
It is a very minor issue, but I'm glad you could reproduce it. Maybe Nvidia can implement some fix in the future.
So long I enjoy the stunning v4 release.
Keep up your excellent work!

Cheers
Andreas

TScottJ
Posts: 2
Joined: Sat Jul 15, 2017 4:22 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby TScottJ » Sat Jul 15, 2017 4:28 pm

I have exactly the same issue (GTX 1080 x 2 in SLI Surround, 5760 x 1080). I noticed the problem does not exist when running FSX SE, for what it's worth. I have two monitors connected to the first GTX 1080, and 1 monitor connected to the 2nd 1080. I'll try connecting all 3 monitors to one 1080, after I buy DisplayPort to HDMI converters. But I think it would be good if you guys (Prepar3D/NVidia) can figure this out.

Disabling Surround is not an option, as this incurs about a 50% FPS hit on my system.

angeli662
Posts: 4
Joined: Thu Jun 26, 2014 12:12 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby angeli662 » Sun Jul 16, 2017 1:46 am

I have 2 1080ti in SLI surround I had the same issues If you haven't resolved here is what found out
Connect all 3 displays to the first card and run the SLI config again. I fixed all the effects including the contrails etc.

Saldo
Posts: 330
Joined: Thu Sep 18, 2014 7:26 am

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby Saldo » Sun Jul 16, 2017 1:32 pm

Exectly , you always need 3 seperate views . Either :
- SLI --> all monitors connected to 1 graphics card with second one in SLI
- Non SLI --> all monitors connected to 1 graphics card

TScottJ
Posts: 2
Joined: Sat Jul 15, 2017 4:22 pm

Re: [P3D v3+4] 2x GTX 1080 + 3x 1440p screens in SLI/Surround = no effects on right monitor

Postby TScottJ » Mon Jul 17, 2017 1:30 pm

I have exactly the same issue (GTX 1080 x 2 in SLI Surround, 5760 x 1080). I noticed the problem does not exist when running FSX SE, for what it's worth. I have two monitors connected to the first GTX 1080, and 1 monitor connected to the 2nd 1080. I'll try connecting all 3 monitors to one 1080, after I buy DisplayPort to HDMI converters. But I think it would be good if you guys (Prepar3D/NVidia) can figure this out.

Disabling Surround is not an option, as this incurs about a 50% FPS hit on my system.
FYI, I bought a $12 DisplayPort to HDMI adapter so now have all 3 monitors plugged into the first GTX 1080 card, and this resolves the issue (as others have noted). Seems I may even be getting slightly better frame rates as well, though that could just be coincidence or my imagination.


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