Interesting article at Tom's Hardware:

To qoute "Earlier this year, NVIDIA drew a lot of flak over a number of questionable optimizations in their drivers for 3DMark 2003 - optimizations which could definitely be called cheats. It was in response to this that NVIDIA came up with the guidelines pertaining to performance optimizations mentioned above. Laudably, we haven't been able to make out any "violations" of the new rules in the new driver v52.16 - at least so far.

ATi, on the other hand, repeatedly claimed that their drivers implemented no illegitimate optimizations. The accusations leveled against ATi at NVIDIA's Editors' Day two days ago thus become that much more serious. Epic's Mark Rein confirmed that in some cases, high-res detail textures were not displayed in some areas by ATi´s drivers and that standard, lower-res textures are used instead. Randy Pitchford of the Halo development team also mentioned that there were optimizations present in ATi's drivers which are detrimental to Halo's image quality. However, Randy didn't want to go into more detail here. Finally, Massive's new DX9 benchmark, AquaMark 3, also displayed some irregularities of ATi drivers in the overdraw test.

Here is a list of accusations we were able to confirm...

www.tomshardware.com/graphic/20031023/nvidia-nv38-nv36-19.html#questionable_optimizations_in_atis_drivers