I don’t think I can as I’m running a barebone (1 PCI, 1 AGP slot)
But it seems you could be right with the IRQs - the sound chip uses IRQ 5 and shares IRQ 7 with USB 2.0. Even if I turn off Plug&Play in BIOS they end up sharing one or another.
How do I manually assign IRQs in BeOS? The only settings in my BIOS are IRQ -> PCI or IRQ -> Reserved