GSX + Level 2 extremely low framerate with two GPU in P3DV4.5

[Camilfly]

Hi all.

I have a new PC with two GPUs (1060 and 1660Ti). I am running P3DV4.5 (HF3) flawlessly with a simulator running PMDG 737NGXu with several monitors connected on the two cards.

I was running all fine, with great FPS (between 30 and 40FPS) with this setup, undocking windows to distribute the panels over my monitors.

That's when I installed GSX and GSX Level 2 and I started having sever FPS drops (2 or 3 FPS) making the sim unflyable.
If I run P3D without undocking windows, no problems, FPS are ok.
When I undock a window, doesn't matter if it's a panel or a view, and move it to another window, FPS drops to 2.
If I uninstall GSX I can undock and move windows without this issue.

Before you suggest this, I already formatted my PC (twice) and reinstalled all add-ons.
I already tested a configuration with just P3D and GSX installed, no other addon, and the problem is immediately evident.
Without GSX, having ORBX sceneries, several airports, REX and PMDG, it runs fine, up to 40FPS.

I also updated all my software, including Windows 10.

This is clearly an issue with GSX and I was wondering if there's an issue with the program running on multiple GPUs and monitors.
Right now, I am flying with GSX uninstalled with no significant performance drops.
My specs:

Core i7 9700K
32GB RAM (2666mhz)
SSD Samsung
GTX 1660ti (external view)
GTX 1060 6GB (instrumentation)
Resolutions 3x 1080p

Any help would be appreciated.
Thanks in advance, Umberto.

[virtuali]

This is clearly an issue with GSX and I was wondering if there's an issue with the program running on multiple GPUs and monitors.

It's clearly NOT a GSX issue, it's a very well known issue with any product that use Render to texture ( GSX happens to be one of the very few that does ), which doesn't work well when a window is docked on another monitor that is connected to a different video card.

This has been discussed many times on the forum and, it can be fixed by checking the "Disable RTT" option in the Addon Manager menu. This will lose jetway logos, jetway numbers and ground vehicles logos, but it's the only way to have GSX running on multiple video cards.

[Camilfly]

Hello Umberto, thanks for your reply and further help. I will test this particular fix and let you know if it worked.

Also, I'm not saying your program is flawed, but if this happens only with GSX installed, then it clearly IS a problem within GSX. We could be discussing semantics all day, let's not. What I wanted was to assure everyone reading this that I am not just shooting blame around.

Thanks.

[Captain Kevin]

But then how many programs do you have that actually uses render to texture.

[virtuali]

but if this happens only with GSX installed, then it clearly IS a problem within GSX. We could be discussing semantics all day, let's not.

The problem is that undocking windows can happen even without GSX, and this is a very well known fact.  If only happens with GSX on YOUR system, doesn't mean it's caused by GSX, it only means you don't have any other software or configuration that trigger this behavior.

See here, for example, on LM forum, a report of fps dropping from 30 to 3 when undocking on a 2nd monitor:

https://www.prepar3d.com/forum/viewtopic.php?f=6312&t=132108&p=191945

Which somebody linked to a possible solution on Avsim, which had more than one thread about it:

https://www.avsim.com/forums/topic/513687-p3dv4-multimonitor-undock-windows-halves-frame-rate
https://www.avsim.com/forums/topic/514478-p3dv4-dockundock-causes-fps-issue/

In neither case the solution was related to GSX.

GSX Render to Texture is only ONE of the several possible reasons of low fps when undocking windows, which is why we have the option to disable it.