As opposed to 3DMark06, 3DMark06 shows a certain advantage of the GeForce 9800 GTX although it is not enough to compete with the ATI Radeon HD 3870 X2 which has as many as 640 shader processors.
Interestingly, the new card enjoys a bigger advantage in the SM2.0 than in the SM3.0 tests although its main and shader domain frequencies are increased proportionally, by about 4%, in comparison with the GeForce 8800 GTS 512MB. Perhaps the first SM2.0 test has lots of memory accesses as it uses numerous light sources and high-resolution textures, including detailed lighting/shadowing maps. And the new card has a higher memory bandwidth than the GeForce 8800 GTS 512MB: 70.4GBps against 62GBps.
The individual SM2.0 tests confirm our supposition. There is indeed a 7-8% performance increase relative to the GeForce 8800 GTS 512MB in the first test, but in the second test the gap is only 4%. So, it is the first test that contributed the most to the overall result.
The GeForce 9800 GTX enjoys a bigger advantage over the GeForce 8800 GTS 512MB in the second test: 8% against 5%. This must be due to the same reason as in the SM2.0 tests: the new card uses faster memory.