Hi, we have a bad problem on the 5850 (only 5000 series board tested). Our application renders a number of textures via FBO and it performs horribly unless we disable mipmaps for these textures. We've tried every combination of glgeneratemipmaps, glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE) or specifying each mipmap level with null pointers, all cause terrible performance. The textures are not generated every frame, the bad performance is from rendering geometry using these textures in a simple shader.
In contrast a 4670 performs a huge 30% faster with mipmaps enabled, the nvidia boards we tested all show a noticeable improvement in performance with mipmaps.
We also have some uncompressed textures that are uploaded every frame and use glgeneratemipmaps, these perform similarly with or without mipmapping. We did notice that the 5850 never seems to perform better with mipmapped textures where all other hardware shows an improvement, normally we don't see significantly worse performance though.
On a side note, if we call glgeneratemipmaps without enabling GL_GENERATE_MIPMAP on the textures then the call brutally crashes.
This is with the latest drivers and also some slightly older ones.
Some help with this issue would be greatly appreciated, we've invested a lot in the technology that relies on these textures.