I don't know what can help with your problem but this may also help : VIA_AC97.866: DOS VIA 686A/B AC'97 init/mixer tool + FM TSR replacement

It is a replacement to VIAFMTSR that a friend of mine is developing which uses modern accurate OPL3 emulation cores for authentic sound and perhaps it won't have the same issue as VIAFMTSR has, or at least can possibly help to tell what it may be.
EDIT: Seems he hasn't actually released it yet, but I can tell that it will be awesome 🤣
His init tool may still be helpful, it definitely improves upon anything else.

Tiido wrote on 2025-03-11, 00:23:

I don't know what can help with your problem but this may also help : VIA_AC97.866: DOS VIA 686A/B AC'97 init/mixer tool + FM TS […]
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I don't know what can help with your problem but this may also help : VIA_AC97.866: DOS VIA 686A/B AC'97 init/mixer tool + FM TSR replacement

It is a replacement to VIAFMTSR that a friend of mine is developing which uses modern accurate OPL3 emulation cores for authentic sound and perhaps it won't have the same issue as VIAFMTSR has, or at least can possibly help to tell what it may be.
EDIT: Seems he hasn't actually released it yet, but I can tell that it will be awesome 🤣
His init tool may still be helpful, it definitely improves upon anything else.

Hello. I looked through the post but it looks like it definitely needs VIAFMTSR to enable FM support and this is where the issue is happening. Using VIAFMTSR, many dos games fail to load including Doom 1/2, Jazz Jackrabbit, Prince of Persia 2, etc.

What is your south bridge? are you sure it supports SB emulation?

VT1612A is your AC97 codec, it doesn't mean your south bridge supports it.

Pino wrote on 2025-03-11, 17:55:

What is your south bridge? are you sure it supports SB emulation?

VT1612A is your AC97 codec, it doesn't mean your south bridge supports it.

My south bridge is 82C686B.

stealthjoe wrote on 2025-03-11, 16:36:

Hello. I looked through the post but it looks like it definitely needs VIAFMTSR to enable FM support and this is where the issue is happening. Using VIAFMTSR, many dos games fail to load including Doom 1/2, Jazz Jackrabbit, Prince of Persia 2, etc.

The modern init tool may help with the problem, as it possibly sets up the actual sound hardware in a more compatible way and perhaps VIAFMTSR will behave better as a result, it won't hurt to try.

I noticed some trace damage on the back side of the motherboard right behind the southbridge. I am thinking if the issues could be due to it.

Trace damage can cause all kinds of problems, so it is better to go over these and make repairs when needed. Few of those traces do look like they have been severed not just scratched.

The strange part is that the DOS games sounds and FM work fine under 98. Under pure DOS mode initializing VIAFMTSR crashes many games. I am yet to find a thread where using VIAFMTSR causes crashes. So it looks like mine is an isolated incident (damaged traces possibly). However on using only SBCFG tool, the sound blaster works fine for most games, but no FM (obviously).