Update: sorted the (upper) memory issue: it was the integrated NIC's bootROM hogging upper memory. With BIOS 1.09 there wasn't anything I could do about it, but after an upgrade to 2.07 (on TheRetroWeb), at boot the network adapter's ROM initialized with option to press Esc for settings. I did so, told it to boot local drives (option 1), after which it apparently unloaded itself. So now I have EMS and NIC.

And...

Both VIAUDIO.COM and VIAFMTSR now work perfectly 😀

It wasn't the EMS though, as even if I do NOEMS or re-enable the boot ROM, VIAUDIO (and VIASBCFG) and VIAFMTSR work perfectly. Conclusion: BIOS 1.09 was borked for legacy SB audio and the upgrade to 2.07 fixed that completely. Hope this info can be of use to others in the future.

For reference, emm386 can unmap that useless (for a dos machine) pxe rom, if you know its exact address range.

You do so by making it an explicit include.

Eg, if it's at D000-D7FF, then force include that range,

I=D000-D7FF

Then you can combine that with the FRAME option, to put the pageframe there.

FRAME=D000

The include MUST NOT overlap another region, or EMM386 will complain every boot. Each region needs to be explicitly included to unmap a rom.

dionb wrote on 2024-12-07, 01:29:

Despite my preference for period-correct old AT stuff I decided I wanted a small, eminently portable DOS system capable of playi […]
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Despite my preference for period-correct old AT stuff I decided I wanted a small, eminently portable DOS system capable of playing just about anything DOS. So I plumped for a Via Epia 800 board and mounted it in a tiny mITX case. Then installed a 256MB PATA DOM with DOS 6.22 on it. HIMEM.SYS and EMM386.EXE NOEMS. After some messing around found the correct packet drivers for the integrated VT6103 LAN: the Rhine driver with FETPKT.COM (note: don't download the drivers from the Via site, even if you choose the correct chipset you get drivers for later Gb NICs that don't work on the Rhine Fast Ethernet). mTCP up and running so I could move stuff around with FTP. So far, so good...

Then it was time to get sound working. First I set A220 I5 D1 P330 in BIOS.

What I expected (based on this topic)
- integrated SB audio in Via VT8231 southbridge will offer good SBPro2 support after initialization, just set correct legacy resources in BIOS
- initialization can be done with VIAUDIO.COM, assuming BIOS version older than 2.x (mine is 1.09)
- FM synth could be emulated with VIAFMTSR.COM

What I experienced:
- VIAUDIO.COM reports correct initialization, but no sound output.
- VIASBCFG.COM did give me good SBPro2 sound
- VIAFMTSR.COM doesn't give me FM with either VIAUDIO.COM or VIASBCFG.COM

I then wondered whether the lack of EMS might be a problem so I changed EMM386.EXE from NOEMS to 4096. That failed with "WARNING: Unable to set page frame base address--EMS unavailable", and Upper memory starting address D600 H. So no space for the EMS page frame. I've disabled all caching/shadowing in BIOS, but almost all memory between 640k and 1MB remains reserved. Not sure if this is what is causing the VIAFMTSR not to work or if it's a separate issue. Any ideas?

Even if you tell the PXE option rom to unload it still uses memory. The USB Keyboard support stack also take up a lot. Make sure to disable that in BIOS setup. I ended up removing the PXE module from the BIOS altogether. That helped a lot.

QEMM 9 also does a really good job of finding UMB on this board. QEMM will also enable you to use SBEMU, which works with the AC97 on these boards.

I also made an open source clone of the USB front port daughterboard, if yours doesn't have one installed: https://github.com/chadr/VIA-EPIA-USB-CV1-Clone

I might still have a few left, I can send one if you cover postage.