Hellbender I'll give you an honest answer as far as I know.
Currently the 6800 in defualt mode only scrimp on AF angles and brilinear.
I believe the angle dependancy is a little better in the 6800 though I haven't really looked to hard into it.
Brilinear vs Trilinear well they both do about the same trilinear/brilinear mix BUT brilinear does favour to use the lower resolution mipmap more then trilinear and the other way around for the higher resoulution mipmap. So their is slight more of a bandwidth save on the 6800 taking into account the texture CACHE.
Now I also belive X800 does another optimisation which the 6800 doesn't I believe that on texture layers 1-7 when AF is enabled it pushes the LOD back further I could be mistaken about this.
6800 does better LOD calculation as well but it doesn't factor in all that much.
Currently the 6800 in defualt mode only scrimp on AF angles and brilinear.
I believe the angle dependancy is a little better in the 6800 though I haven't really looked to hard into it.
Brilinear vs Trilinear well they both do about the same trilinear/brilinear mix BUT brilinear does favour to use the lower resolution mipmap more then trilinear and the other way around for the higher resoulution mipmap. So their is slight more of a bandwidth save on the 6800 taking into account the texture CACHE.
Now I also belive X800 does another optimisation which the 6800 doesn't I believe that on texture layers 1-7 when AF is enabled it pushes the LOD back further I could be mistaken about this.
6800 does better LOD calculation as well but it doesn't factor in all that much.