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jam_mer
11-23-2010, 04:33 AM
Hi,
I've recently got ATI Radeon 5970 and I tried to run some of my OpenGL programs in crossfire mode. I was disappointed when it came to compare performance with CF on/off - no difference. I've tried various tweaks to force CF to work:
- rename to etqw.exe: crash, GLEW failed to initialize
- create custom profiles using RadeonPro: no difference, however I noticed slight improvment with Supertiling method

I've tried this on simple (basic per-pixel lighting) as well on complex programs (HDR render with AO and shadows, GPGPU calculations) with no effect (looks like only one GPU is working). In DirectX11 apps, speedup was almost 1,9x.

Is there something else to do? Or everything we can do is to wait when finally ATI improves their drivers and enables us to choose manually CF profiles?

Thanks

aqnuep
11-23-2010, 07:17 AM
I don't know how much IHVs concentrate on automatic SLI/CrossFire support for OpenGL apps. However, you can explicitly take over the power of your CrossFire config with the WGL_AMD_gpu_association / GLX_AMD_gpu_association extensions that allow you to create an affinity context on a dedicated GPU.

jam_mer
11-24-2010, 02:20 AM
Yes, I know about these extensions and I'm planning to use them anyway. I was just asking if it's some other way how to force it to work without major changes in code...

aqnuep
11-24-2010, 02:57 AM
Automatic SLI/CrossFire workload distribution is up to the driver. However, as I said, vendors are not really concentrate on SLI/CrossFire support for OpenGL AFAIK.