Which specific model Aureal Vortex PCI sound cards have you tested in real DOS?
And which DOS games worked on it to generate the digital voice or sound effects?
The FM or MIDI isn't essential at the moment if a PCIe MPU-401 could be designed to deal with that separately.
AU8820 (Montego A3DXstream) was the one I tested working, on a P31 board, both digital voice and sound effects in some games (I mainly tested Wolf3D and Terminal Velocity at that time). FM quality isn't good, though.
I once attempted running AU8830 (Montego II) on a G41 board, but probably due to some PCI resource issues or configuration error, I wasn't able to get that working (only the MIDI daughtercard worked), but it should in theory work if configured properly.
Could you explain more about this daughtercard. Does this insert into the Aureal Vortex sound card? And what drivers (Config.sys, Autoexec.bat, TSRs) need to be preloaded for it to work properly in real DOS.
NEC XR385 is a Wave Blaster compatible daughtercard that you can just plug it into the PCI audio card's wavetable header, and it'll work (you'll be able to hear music if you configure the game to use General Midi 330h), without any additional configuration.
This might be true but modern chipsets can now drop down to 800 MHz. Previously it was 1600 MHz. I will attempt to get BIOS manufacturers to try and include further downclocking potential to 400MHz, 200MHz, 100MHz, 66MHz, and 33MHz if this is somehow possible. I don't think below 33MHz will be achievable.
But if you take into account the CPU utilization requirements of DOSBOX itself combined with MUNT it will actually kind of act like a slowdown utility in hardware mode.
I don't think I could actually underclock the CPU to the point of being retro-friendly on modern boards. Some Socket 370 boards allows me to underclock the FSB to 66Mhz from 133Mhz, allowing me to play the problematic games (e.g. Thor's Hammer Trilogy) while retaining the ability to use Windows 9x/XP at high performance.
Most CPU slowdown utilities (such as Mo'Slo) could not reduce the reported clock speed to match the slowdown target, and this can cause issues with some games that have behaviors tied to reported CPU clock speed. In such cases, using Mo'Slo would also slow down aspects that shouldn't be slowed. (Thor's Hammer Trilogy was unfortunately one such example. With Mo'Slo, while it could make gameplay behave properly, it also slowed the title and menu screens which don't need to be slowed to the point of taking forever to complete)
What do you mean by native PCI? Are you saying PCI slots don't function the same as in the 386?
The last DOS SB emulation sound card that I did test that worked properly was on a Pentium 1 relic. But it depended on Himem.sys and EMM386 which no longer function properly since SkyLake and possibly as early as Haswell.
At the moment you can still find PCI slots from Z68 to Z370 and AM4 for AMD users. These are quite rare to find as time goes on which is why eventually an adaptation of a PCI chipset that works in DOS to a PCIe card form will be its salvation. I believe the PCIe slot will still be around 10 years from now after the PCI slot has gone extinct.
Only PCHs starting with B or Q provided PCI slots on its own (thus native PCI) for a while, others did not, and instead used PCIe-to-PCI bridges to provide PCI slots.
The last chipsets known to natively provide PCI were B75 and Q77. Starting from 8 Series, the PCH stopped providing native PCI slots completely.
Subtractive decoding on the PCIe-to-PCI bridge is required to enable the ability to access legacy resources (which are always below the PCI card's base I/O address). Otherwise, the audio card's legacy functionality (such as FM synth @ 388h) will not function, even under Windows or Linux.
I don't know much about AMD chipsets, but PCI audio cards never worked under DOS with AMD chipsets since 700 series. You can successfully load TSRs, but games still won't be able to detect the card at all, which probably indicates a lacking of subtractive decoding on the PCI slots (native or not), so games couldn't "see" the emulated Sound Blaster.