Hmm.........
@ Goldi: Yaar listen....... you know the effect fog has at greater distances. The X800 is not capable of using SM3.0, therefore that effect is not showing which was probably implemented using SM3.0 specific instructions.
@ Rave: 9800 XYZ core do now support SM3.0. Hence you cannot notice the difference.
Also, these games are highly optimized to the extent of using different code paths for differnet VPUs. So when you change the device ID to 9800pro, you are making the game execute a code path which was optimized for a 9800pro and not a 6xxx series card. Both the cards are very different as they perform differently under different instructions. So when you forced a code optimized for a different VPU to run on a 6600GT, you got suboptimal performance. As simple as that...........
To ensure that I am not speaking crap..... fire up ur copy of Doom3 and switch different code paths and see the fps difference. The one optimized for ur VPU will give max fps/quality and all others (while they will RUN as they make use of OpenGL 1.5) will have some quality+fps tradeoffs.
IN MY HONOURABLE OPINION: The SM3.0 image looks more realistic to the extent of being 3> than the X800 image. Mind you, I own a 9800xt currently so I have no reason to be biased.
Cheers,
Karan