Several weeks ago I wrote an article about how to enable SLI / CF for OpenGL applications. Today, the article shows some other tips for enabling SLI and CrossFire support for MSI Kombustor. Of course, these tips are also valid for other OpenGL apps like FurMark, TessMark or your own OpenGL demo!

1 – How to enable SLI support for GeForce cards

MSI GTX 460 Cyclone, 2-way SLI

For simple OpenGL applications, just follow the steps described HERE. But for MSI Kombustor, tweaking SLI in NVIDIA control panel is not enough to get the most of your GPUs because of the post processing. If you run KMark in 1080 preset, a 2-way SLI system will have a lower score than a single GPU system. With default settings, NVIDIA drivers are not able to properly handle OpenGL scenes with post processing effects (via FBO / render to texture or RTT). It’s not a bug in the driver but rather a matter of politics or something like this.

Even if you follow (and I followed) NVIDIA’s guide (SLI Best Practices), your application is not still able to fully exploit SLI. For example, a single GTX 460 has a score of 1505 points (32FPS) in KMark Preset Extreme (KMark is Kombustor OpenGL 4 benchmark) while two GTX 460 in SLI have a score of 1367 points (20 FPS) for the same preset.

Then what is the solution?

Simply tweaking the NVIDIA profile with GeForce 3D Settings Profile Manager. This tool, developed by NVIDIA, allows to export and import the profile file. The profile file is a simple text file anyone can edit with a simple text editor. Here is a profile that works fine for MSI Kombustor and allows to take advantage of n-way SLI up to four GPUs:

Profile "MSI Kombustor"
    ShowOn GeForce
    ProfileType Application
    Executable "MSIKombustorDX9.exe"
    Executable "MSIKombustorDX10.exe"
    Executable "MSIKombustorDX11.exe"
    Setting ID_0x00a06946 = 0x084000f5
    Setting ID_0x1033cec1 = 0x00000003
    Setting ID_0x1033cec2 = 0x00000002
    Setting ID_0x1033dcd2 = 0x00000004
    Setting ID_0x1033dcd3 = 0x00000004
    Setting ID_0x1095def8 = 0x02c00005
    Setting ID_0x20441369 = 0x00000001
    Setting ID_0x209746c1 = 0x04280001
    Setting ID_0x20ebd7b8 = 0x00000020
EndProfile

Just copy and paste this profile in NVIDIA profile file and import it with the GeForce 3D Settings Profile Manager utility.

KMark, OpenGL 4, Preset 1080, GPU PhysX

2370 points (60 FPS) – GTX 460 2-way SLI with profile

1505 points (32 FPS) – GTX 460 single

1367 points (20 FPS) – GTX 460 2-way SLI without profile

MSI Kombustor, burn-in test

Burn-in test, OpenGL 2, 1920×1080 fullscreen, no AA, Post FX Off

4102 points (68 FPS) – GTX 460 SLI with profile

2063 points (34 FPS) – GTX 460 single

Burn-in test, OpenGL 2, 1920×1080 fullscreen, no AA, Post FX On

2076 points (35 FPS) – GTX 460 SLI with profile

1042 points (17 FPS) – GTX 460 single

MSI Kombustor burn-in test – SLI is properly exploited in OpenGL 2 + PostFX with the new profile

2 – How to enable CrossFire support for Radeon cards

SAPPHIRE Radeon HD 6970 in 2-way CrossFire

CrossFire is AMD’s multi-GPU technology for Radeon graphics cards. Since Catalyst 11.2 (and maybe Cat11.1), AMD’s graphic drivers come with a CrossFire profile for FurMark. And since MSI Kombustor and FurMark have some code in common, you can rename MSIKombustorXXX.exe in FurMark.exe without problem 😉

Here are some scores for a Radeon HD 6970.

KMark, OpenGL 4, Preset 1080, CPU PhysX

2414 points (52 FPS) – HD 6970 CrossFire

1406 points (41 FPS) – HD 6970 single

Burn-in test, OpenGL 2, 1920×1080 fullscreen, no AA, no Post FX

7987 points (113 FPS) – HD 6970 CrossFire

4147 points (69 FPS) – HD 6970 single