prccowboy posted this over at https://forums.eagle.ru/showpost.php?p=3410823&postcount=65
Since I started this thread, I felt compelled to write this post as a guide to others trying to get SLI to work in DCS2.5
Note: these settings work with the 2.5 Release build (184.108.40.20665.345); however, the 2.5.1 Open beta build may have reintroduced a cloud flicker problem ==> Update: flicker fixed in 220.127.116.1135
DCS doesn’t have a working SLI profile from Nvidia. You will need to change the default profile to get SLI working properly.
First, make certain that you have SLI enabled in the Nvidia Control Panel. (3D Settings=>Configure SLI, Surround, PhysX=>Click “Maximize 3d performance” under SLI configuration)
Next, make sure that Nvidia Control Panel (NVCP) recognizes DCS (3D Settings=>Manage 3D settings=>Program Settings Tab=>Select a program to customize=>Digital Combat Simulator: Black Shark) Don’t worry about the “Black Shark” part, all versions of DCS use this profile. If NVCP doesn’t have this program listed, you will need to add it manually (“Add” then “Browse” to find the DCS program. Example: “F:>Program Files>Eagle Dynamics>DCS World>bin” and “DCS.exe”)
This will load the default Nvidia profile which does NOT work. You will need to change the profile.
To modify the profile, you need “NVIDIA Profile Inspector” by Orbmu2k (NVI)
Once you have started NVI, Select the “Digital Combat Simulator: Black Shark” profile. Next change the “SLI compatibility bits (DX10 + DX11) setting to “0x080600F5 (S.T.A.L.K.E.R.: Call of Pripyat)”. You may also have good results using other settings like “0x081000F5 (Dirt 3, Dirt Rally)” but some (myself included) have reported cloud flickering problems with those bits
The other SLI setting that you might need to change is the “Nvidia predefined SLI mode on DirectX 10”. I have best results (fps) with “AUTOSELECT” but others use “FORCE_AFR” or “FORCE_AFR2” (I also used AFR2 before 2.5)
Don’t forget to click “Apply Settings”
Now SLI works in DCS, Enjoy the extra GPU power !
Note: In game, you might need to use L-Alt+Enter to switch to full screen exclusive while playing to see the full benefits.
Just because you now have SLI working and (theoretically) double the GPU power, it doesn’t mean that you will see FPS boost everywhere. CPU and GPU performance is related. To those thinking “my cpu utilization is less than 25% and/or I have affinity set to all cores, so I’m not cpu bottlenecked.” Well, you are probably wrong. It has been stated many times in other threads that DCS really only utilizes 2 cpu cores (with some additional threads being spread to other cores by Windows). If you have periods where your gpu utilization drops, then most likely one of your cpu cores just got maxed out (but the other cores are underutilized so overall it looks like your cpu is not the bottleneck).
In post #40, https://forums.eagle.ru/showpost.php?p=3408608&postcount=40, I show how your framerates can be bottlenecked by either CPU or GPU:
There are some good guides to optimization:
However, I want to suggest that if your gpu’s show low utilization but you still want more FPS, try reducing “Visible Range.” This is one of the easiest ways to reduce CPU load and let it catch up to your GPU’s. In the end, I dropped my visible range and overclocked my CPU (but I know that’s not for everyone)