Standard Video Modes
The following results are from the standard Quake 3 video modes which consist of:
- Fastest - 512x384 - 16-bit color - vertext lighting
- Fast - 512x384 - 16-bit color - lightmap lighting
- Normal - 640x480 - 32-bit color - lightmap lighting
- High Quality - 800x600 - 32-bit color - lightmap lighting
Note that the Normal mode uses a default color depth and is determined by the color depth of your desktop, which in this case was 32-bit color. There are additional settings in each of the modes that are not listed.
The Fastest mode uses vertex lighting, or a poor man's lighting, and is an option best used for graphics cards that cannot multitexture. Vertex lighting is not "true" OpenGL lighting, and is not accelerated by the GeForce. GeForce owners should use lightmap lighting.
Vertex Lighting
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Lightmap Lighting
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Quake 3 Demo001 - Standard Video Modes

The high quality results (60 fps) on a P2-450MHz at the GeForce 256's default clock speeds of 120MHz/166MHz are impressive considering that a TNT2 manages to get around 35-40 frames per second on a P3-504MHz.
Overclocking Results
Playing Quake 3 under high quality settings, which includes 32-bit color, is extremely demanding even on today's fastest PCs. Take a look at the following benchmark results using high quality settings at three overclocked core and memory clock speeds:
Quake 3 Demo001 - High Quality - 32-Bit Color

Performance improves in 16-bit color (chart below), primarily at resolutions greater than 800x600, due to the decrease in memory bandwidth compared to 32-bit color. However, many TNT/GeForce owners prefer to play Quake 3 in 32-bit color (see poll results).
Quake 3 Demo001 - High Quality - 16-Bit Color

Let's Tweak
Fortunately, there are a variety of graphics settings that can used to speed up game play at the expense of less eye candy. Unfortunately, with the number of graphics settings that can be configured, including the permutations within those settings, it becomes extremely time consuming to benchmark every aspect of Quake 3.
In addition, each player has their own preferences. Some opt for the highest frame rates, at the expense of less eye candy, while others want to balance the two. Even the phrase high frame rates is a point that's been endlessly debated. Suffice it to say that it means different things to different players. While 40 frames per second is acceptable performance for some players, 60, 80, or even 100 fps is a requirement for others. Different strokes, for different folks.
I've taken Quake 3 benchmarks a step further and include results from four different settings to give the reader, and myself, a better understanding of performance. The first setting, S1, represents the standard high quality settings used in Quake 3. Each subsequent setting, S2 through S4, takes away a bit more eye candy.
Note that the results from the S1 setting in 16-bit color used 16-bit texture detail, while results in 32-bit color used 32-bit texture detail (which is the default under high quality settings).
The results were run on a Pentium 2-450MHz/128MB RAM/GeForce 256 SDR overclocked to 145MHz/190MHz using NVIDIA's version 3.53 reference drivers. Sound and vsync were disabled.
Tweaked Settings
Setting 1 - S1:
- High quality settings: 16 or 32-bit color depth, fullscreen on, lightmap lightmap, medium geometry detail, texture detail 3, 16 or 32-bit texture quality, trilinear texture filtering
Setting 2 - S2:
- Setting 1 with all game options disabled (simple items, marks on walls, ejecting brass, dynamic lights, identify target, and high quality sky)
Setting 3 - S3:
- Setting 2 with the following options disabled: drawattacker, draw3dicons, gibs, and shadows
Setting 4 - S4:
- Setting 3 with low geometric detail, bilinear texture filtering, and 16-bit texture quality (which was used in 16-bit color benchmarks)
For a list of Quake 3 graphics settings, be sure to check out this page at Quakeheads.com.
Quake 3 Demo001 - Tweaked Settings 1-4

Final Comments
The good news for those who prefer to play in 32-bit color is that the high quality settings (S1) at both 640x480 and 800x600 provided at least 60-70 frames per second. The bad news is that at 1024x768, the GeForce 256 SDR only manages to pump out a meager 47 fps.
There are a few things I can do at this point to reach the magical 60 fps at 1024x768 in 32-bit color: with a GeForce 256 SDR, I can use settings 3 or 4, or upgrade to a GeForce 256 DDR, which will come close, or exceed with a faster processor, to reaching 60 fps using high quality settings.
Playing in 16-bit color at all resolutions provided at least 60 fps. At this point, the best bang for the buck to get significantly higher frame rates, would be changing to setting 2. Settings 3 and 4 aren't really necessary at this point.