mipmapped texture are extremely efficient in our HW, so you must be running in some unexpected behavior which is causing significant over validation. the only time where I can see a big CPU overhead is when we actually generate the mipmap, but if that does not happen every frame, then it should not be an issue.
the best way to find out the issue is to send a simple test case to our devrel team, and put my name in CC.
Normally, yes. I was generally impressed with the card's texture fill perf, something is obviously very wrong here but we're hardly doing anything exotic. It hadn't occured to me that it could be a CPU overhead until you mentioned the CPU. It seems that CPU usage does indeed increase dramatically with mipmapping enabled. We also tested a number of other drivers and found that the problem was worse in OGL 3.2 drivers, 10.3a preview and 10.3 WHQL both performed significantly worse with the mipmaps than 10.3 OGL4 preview, for example. The radeon 4670 has a gl 3.2 driver though and that's much faster with mipmaps than without.
Any idea why mipmapping in general doesn't _improve_ performance? Non mipmapped texture performance matching or exceeding mipmapped performance for large textures strikes me as impossible. Also I thought the 4670 and the 5850 weren't all that different?
Anyway, how exactly do I contact your devrel team? Posting in a public forum would not have been my first choice but I couldn't find anything else. I used to have a contact but it's been some years now. I'll see about putting a test app together.
Thanks for the help. I also wanted to say that I really appreciate how much your opengl support has improved recently, besides this problem development on recent radeons has been a breeze, everything seems to work and really well.