At the resolution of 1024x768 there are only small differences between the various Pentium III types. nVIDIA's GeForce 2 MX is definitely acting as the bottleneck, as the frame rates does not increase with faster CPU clock rates. GeForce 2 GTS and Ultra perform much better, but even with the GTS you can see its fill rate limitation when using the Pentium III 933. Between 733 and 866 MHz, the frame rate increased by 4 fps, but only by 2 fps between 866 and 933 MHz.
Quake III Arena: 1600x1200
At the top resolution of 1600x1200 a Pentium III 800 demonstrates quite sufficient performance. Greater CPU power has no effect on Quake III frame rates. Even the mighty GeForce 2 Ultra is limiting the theoretical frame rate.