I've just upgraded my dev machine to a (Sapphire 1GB) 6870 and I'm seeing a massive slowdown with OpenGL applications.
Previous video card was 4850 and happily ran one of our OpenGL demos at ~30fps.
With 6870 the demo runs at ~7fps.
I've tested with ATI Mecha demo (which AFAIK is Direct X) and framerate is fine.
To eliminate our demo as the problem I tested with http://rastergrid.com/blog/downloads/mountains-demo/
and also several demos from this site: http://magnum.dimajix.de/download/demos.shtml
I've also tried this with a completely clean install of windows to eliminate the chance of any 3rd party applications affecting this.
All of them seem to be experiencing similar problems with performance but DX applications run smoothly.
In the past on other cards I've debugged the video driver to see if something has fallen into software but I don't recall anything being as glaringly bad as this - is there anything which is not being supported correctly in hardware for 6870 or any other known issues with the OpenGL implementation for this card?
ATI Drivers version 12.1 / Windows 7 64bit / 4 GB ram / AMD Phenom X6