Hi everyone,

 

With P3D people have reported a significent bootst in fps when using this tweak.

The only drawback seems that several addons seem not compatible with it  ( t.i.  : they need p3d.exe ).

 

Before trying it in FSX I was wondering if anyone of you alreay tried it and perhaps could give some feedback.

 

Here how it was advised for P3d

Make a copy of your Prepar3D.exe file and rename it AFR-Friendly.exe.

This is a developertrick for telling the SLI drivers not to copy any resources between each GPUs frame. 

Any timeyou disable/enable SLI in the driver settings you should clear your shader cache or you may get driver crashes.

 

NVI

Antialiasing..........AA_mode_selector_SLIAA_Enabled

# of GPU's.......    SLI_GPU_Count_Two

SLI Rendering......SLI_Rendering_Mode_Force_AFR2

 

Nvidia Control Panel

SLI Enabled

 

 

All input is welcome.

No one using 2 graphics cards in SLI ?

Following! Great question!

http://forum.avsim.net/topic/449244-2-way-and-3-way-sli-support-in-p3d-v23/

Following! Great question!

 

http://forum.avsim.net/topic/449244-2-way-and-3-way-sli-support-in-p3d-v23/

That topic I am also following.

 

If Rob finds a good config then that can be used as a base for FSX.

P3D will benefit more as several processes are now done by the graphics card instead of the cpu as in FSX.

GSalden, this isn't quite clear to me.  Are you getting x percent more fps with this "tweak".  Do we need to rename the fsx.exe to something else, or do we just set those 3 things in Nvidia inspector?  If so, I don't understand the point of renaming the exec, so if you could explain that a bit...

Does not work with ATI crossfire. Tried it a couple of years ago when it was a hot topic then. Actually makes things worse. As a matter of fact its been mentioned numerous times to not even run your cards crossfired, period, when running fsx.

http://developer.download.nvidia.com/whitepapers/2011/SLI_Best_Practices_2011_Feb.pdf

After reading the link, I still don't understand what renaming prepar3d.exe (or fsx.exe) to AFR-Friendly.exe is accomplishing here.  I have no idea how doing this and simply running FSX under a different name causes the resources not to be copied between each frame.

 

***I noticed that the most obvious way to set the SLIAA setting is in the Nvidia Control Panel.  In Nvidia Inspector, you can set Enable SLIAA, but when trying to set the actual settting, it is not clear what should be selected.  By setting SLI 8x in the Nvidia Control panel, however, applying it, and then opening up Nvidia Inspector, it will set the AA level to 4x, which I deduce is that each card is doing 4x antialiasing.  Likewise choosing SLI 16x in Control panel, will set Nvidia Insp. to 8x. ***

It's not exactly in plain English:

 

 

Testing the AFR Scaling Potential of your Application

 

Before spending any time trying to resolve the mentioned pitfalls, developers of Direct3D applications can take advantage of a feature in the NVIDIA driver that allows them to check the maximum possible scaling in a given SLI configuration. When running on a system with multiple GPUs configured in SLI mode, simply running your application executable renamed as “AFR-FriendlyD3D.exe” will make the driver skip any form of inter-GPU synchronizations, as well as common forms of CPU-GPU synchronization. This will lead to the maximum expected scaling in that system, but may introduce rendering artifacts (since the driver is no longer performing all the operations required to guarantee correctness in AFR mode). Lack of scaling in this case typically indicates the application is CPU bound.

 

In some cases, this approach changes the behavior of the application such that it may not reflect its real AFR scaling potential. In those cases it is possible that either adding an SLI profile, or following the advice in the following sections, or a combination of both, may still result in good performance scaling.

 

It's just a programming "trick" to see how code that is not optimized for SLI will scale with multiple GPUs. It's really not meant as a workaround for end users.

When exploring some of these settings, I noticed the default NVI profile for FSX was already set to Force AFR2 for SLI, so the only variable here was enabling the SLIAA.  I've traditionally set my AA to 8xs before.  Here, I experimented with SLI 8x and SLI 16x.  The original 8xs looks a little better than the specific SLI modes I tried, which could be selected from within Nvidia Control Panel.  In performance, I'm not perceiving much difference, probably because at the level of 8xs it really isn't stressing things out too much in the first place.  

 

I'm not entirely clear on what is happening if I specify 8xS + SLIAA Enabled in Nvidia Inspector alone, because when I select SLI 8x in Control Panel, it specifically sets it to just plain old 8x when viewing it NI.   I don't know if 8xS is a valid combination to use in conjunction with SLI anti-aliasing.  It's probably just ignoring the SLI Enabled setting altogether.