Apologies for necroing an old thread but I've been playing around with an original S3 ViRGE and I asked ChatGPT whether it could write a small C program that automatically checks and corrects invalid checksums for ROM files. After a little back and forth it came up with the attached which worked for me- much quicker than doing it manually. Included is the C file as well as a macOS (Intel) and a Win32 console versions.

Very useful thank you!

Sorry for the bump.
I have revised interest on s3 older cards.
So far what we know is this:

Bios 1.01.03 has the brightness bug at least the version I have and it supports just VBE 1.2.

Bios 2.01.07 hasn't brightness bug and it supports VBE 2.0
Bios layout and mclkconv from wbc: Re: How do I flash VBIOS on an S3 card?
One more thing, v3/4/5 with VBE 2.0 disable 8x14 font which SimAnt and SimCity require to show fonts right.
Bios v1 (1.01.03, VBE 1.2) has 8x14 fonts compatibility, while newer ones do not.
Source: Re: S3 AGP Cards (and possibly others) Too Bright

Bios 2.01.16 is the latest bios released for ViRGE/DX and GX which has the brightness bug and apparently it doesn't follow the general structure of the 07 bios, according to my previous test the frequency is 45mhz 55mhz. I'm trying to tamper it to fix the brightness bug without success so far. The mclk values are located at CD-CE (still unclear) instead of C2-C3.

This is how the frequency is obtained using m, n, r: MCLK = (M+2) / (N+2) × 14.31818 / 2^R MHz
Those are the limits for the values:
135MHz < 2^R × 14.31818MHz < 270MHz
1 ≤ M ≤ 127
1 ≤ N ≤ 31
0 ≤ R ≤ 3
Apparently the fastest cards (35ns memory) are able to handle 83mhz, but it's important to check for memory errors on windows (95\98) since it's more demanding than the old dos and look for memory character corruption.

In my opinion it would be important to be able to have bios versions without the britghtness bug. The problem is that apparently noone so far was able (or willing) to fix the bios bits to correct it and the only solutions are software.

Some utilities for s3 cards:
S3VBEFIX: https://github.com/wbcbz7/S3VBEFIX
MCLK 094a to overclock s3 cards: https://www.geocities.ws/liaor2/myutil/myutil.html
MCLK Useful information: https://www.geocities.ws/liaor2/myutil/mclk.html
SVBL (Shadow Video BIOS loader), a small utility which loads video BIOS from image to shadow memory: Re: S3 AGP Cards (and possibly others) Too Bright
S3 Trio bios collection and information: https://dosdays.co.uk/topics/Manufacturers/s3_trio.php
S3 Virge bios collection and information: https://dosdays.co.uk/topics/Manufacturers/s3_virge.php

Various vogons forum topics on the matter:
S3 AGP Cards (and possibly others) Too Bright: S3 AGP Cards (and possibly others) Too Bright
How do I flash VBIOS on an S3 card? How do I flash VBIOS on an S3 card?
S3 ViRGE BIOS RAM timings S3 ViRGE BIOS RAM timings
S3VBEFIX topic: S3VBEFIX - PC\MS-DOS TSR fix for S3 VESA 2.0 video BIOS