hi martok, thanks for your comment.

I did not know about the performance differences and I'll try to find out more.
I used only the latest 2.4 SDK (custom build pyopencl) so it's time for me to
compile diffent pyopencls with the diff SDK versions. I ll post some info soon.

I can just mentoin that I am a little bit disapointed about the HD6990/SDK 2.4
performance (I think there was a design change of the vector calculation 'core')
so I realy expected 2x speed (compared to 5970) (core/core).

After all I can also tell you that I am so sick of the way AMD threats their
customers. The opencl/cal forum is not moderated and is more a bad joke.
If the cards where not that fast compared to nvidia I would completly ignore
amd (gpus). for them is just a marketing feature not even supporting the
academic researches by just some damn open source - so we can all find out
our self. sorry for drifting out of topic but i just checked the amd forum - of
course there is no info about the different SDK speeds.

happy computing

PS. additional info to my hardware

I got 0 monitors attached
I did not use a crossfire cable