Have you set your BIOS for "PNP or Plug-and-Play Aware OS" --> Yes? This option lets Windows control IRQ, DMA, etc. If set to no, the BIOS assigns all resources. The "NO" setting can cause the sort of resource conflicts you're experiencing.

What other expansion cards do you have installed? You're only using 1 Sound Blaster at a time, correct? Which version of VIA's 4-in-1 Chipset drivers have you installed?

If you're still stuck and feel like reinstalling as a last resort, another option you can check in the BIOS is for "ACPI Aware" or something like this option. Set this to --> NO for Windows 98 and earlier. This will free up IRQ9, among other things. You should rarely need to go this far (more of a preference or concerns with stability). It's possible to edit the registry to revert ACPI, but I avoid such nonsense with Windows 9X. Most hardware or BIOS changes require a reinstall for my builds, so I better get it right the first time.

Yeah, I did. That's why I gave up on my socket 370 workstation board for Windows 98. It worked without issues in XP, but had a resource conflict with AGP graphics cards in Windows 98 which left me without 3D acceleration. Finding drivers was already a challenge because of the origin/intended use case of the board and nothing I did in the otherwise limited BIOS helped either.

Meatball wrote on 2022-03-03, 17:52:

Have you set your BIOS for "PNP or Plug-and-Play Aware OS" --> Yes? This option lets Windows control IRQ, DMA, etc. If set to no, the BIOS assigns all resources. The "NO" setting can cause the sort of resource conflicts you're experiencing.

Yes, the "Plug and Play O/S" Option is set to "Yes".

Meatball wrote on 2022-03-03, 17:52:

What other expansion cards do you have installed? You're only using 1 Sound Blaster at a time, correct? Which version of VIA's 4-in-1 Chipset drivers have you installed?

There is also a Realtek RTL8139B PCI NIC and a ATI Rage 128 Pro AGP GPU. But removing the NIC or exchanging the GPU for another one didn't help.
I'm only using one Sound Blaster at a time.
I used version 437 of the VIA 4in1 drivers.

Meatball wrote on 2022-03-03, 17:52:

If you're still stuck and feel like reinstalling as a last resort, another option you can check in the BIOS is for "ACPI Aware" or something like this option. Set this to --> NO for Windows 98 and earlier. This will free up IRQ9, among other things. You should rarely need to go this far (more of a preference or concerns with stability). It's possible to edit the registry to revert ACPI, but I avoid such nonsense with Windows 9X. Most hardware or BIOS changes require a reinstall for my builds, so I better get it right the first time.

There is no option with "ACPI" in its name but there is a "Power Management" option. I will try installing Windows 98 on a different hard disk with this option turned off.

RandomStranger wrote on 2022-03-03, 19:01:

Yeah, I did. That's why I gave up on my socket 370 workstation board for Windows 98. It worked without issues in XP, but had a resource conflict with AGP graphics cards in Windows 98 which left me without 3D acceleration. Finding drivers was already a challenge because of the origin/intended use case of the board and nothing I did in the otherwise limited BIOS helped either.

If reinstalling Windows 98 doesn't help, I will try Windows XP and see if that works.
I still have my K6 for Windows 98.