VOGONS

My experience with CMI8738 and DOS

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First post, by wbahnassi

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Hi guys,

I'm rebuilding a system based on the M571 Socket7 motherboard. This one:

https://theretroweb.com/motherboards/s/pcchips-m571lmr-v5-1

It has on-board SoundPro chip which is CMI8738 connected directly on PCI slot 3. As I was aiming to build a minimal PC, I thought I'd give this audio chip a chance at proving itself on DOS. Having read people's experiences with CMI8738:

Cmedia CMI8738 - maybe its Biggest Secret

I wanted to listen to its OPL3 quality, and see how far can its SB16 part work with games.

Here is what I have found so far. I downloaded several audio drivers for CMI8738, but it seems they all go back to a v1.9 of SETAUDIO.COM.

Upon first install, it found my PCI IRQ on 0B (11) and remapped it to IRQ5.

First experience, FM was immediatelly playing nicely for all games. I have an ear for original OPL3, and this chip is right on. Very cool!

Digital audio -on the otherhand- almost never worked, or worked for one sfx then caused a hang. After some investigations, I found someone on YouTube trying a card with CMI8738 and mentioning he had better success when he moved the card to a slot that got assigned PCI IRQ 5.
This was not something I could exactly do with an on-board chip, so I went to the BIOS and assigned IRQ11 to ISA instead of PnP. This drove the board to give the sound chip IRQ9. After chasing all the alternative IRQs the board picks and disabling them, I finally cornered it to choose IRQ5 for the PCI IRQ of the sound chip.

Indeed, with this applied, many more games worked with SB16 sfx. And I was even able to drive the PCI IRQ to be IRQ7 for the sound chip, to which SETAUDIO.COM responded by also choosing IRQ7 for the SB16.. Very nice for certain older games..

With this setup, I typed MEM /C /P and interestingly I couldn't see any TSR related to the C-Media.. conventional memory was untouched.

The bad part is that even after all this juggling, digital playback still has some major issues. In Prince of Persia 1, the footstep sounds will keep looping even if prince is not moving. Very annoying. In Terminator 2029, the man in the intro speaks then the intro hangs after he's done his line.
Doom and Doom 2 crash on load...
What a let down... I really liked that this chip can do SB16 and SBPro emulation.. alas it failed my compatibility tests.

Unfortunately I will have to install a proper sound card, and I have a Sound Blaster AWE 64 CT4500 card that is not part of any system yet.. so I installed it. But I really don't like CQM FM..

So I made a little stunt.. I routed the on-board line-out to the AWE64 Aux1 input, and directed SETAUDIO.COM to use stupid addresses for everything except FM...

This way, all games will use the AWE64 digital and midi parts, but when they address FM, they will get their answer from the CMI8738 instead of CQM.

With this, all games were indeed now doing sfx via the AWE64 and FM via the CMI8738. The sound is still fully output from the AWE64, since the CMI8738 is feeding its signal to the AWE64's Aux1 input. I feel I got the best of the two worlds: AWE64 with SB16 native support, plus FM that sounds like real OPL3.

I haven't fully given up on the CMI8738 SB16 part.. I'm wondering if these issues are truly bad SB16 emulation in the chip, or a config problem.. Is DDMA involved? Does my motherboard support it? How does SETAUDIO.COM reside in memory without MEM being able to see it? Why Doom totally crashes?

Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, Speedstar 24X, SB 1.5, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti

Reply 1 of 8, by RetroPCCupboard

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That's cool. I recently bought a low profile PCI card with this sound chip. I haven't yet tried it but my thinking was that I could make a thin Win98 / DOS PC using a micro atx low profile case. Probably with low profile Geforce 4 MX440 or an ATI X300.

If your case though, I am not sure I understand why you would use this sound chip at all. You have ISA slots, so could just use a soundcard that has OPL3, rather than use the AWE64?

Reply 2 of 8, by marxveix

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RetroPCCupboard wrote on 2026-01-11, 22:31:

If your case though, I am not sure I understand why you would use this sound chip at all. You have ISA slots, so could just use a soundcard that has OPL3, rather than use the AWE64?

You use what you have and if everything works as you like, why not.

Best ATi Rage3 drivers for 3DCIF / Direct3D / OpenGL / DVD : ATi RagePro drivers and software
30+MiniGL / OpenGL Win 9x dll files for all ATi Rage3 cards : Re: ATi RagePro OpenGL files

Reply 3 of 8, by RetroPCCupboard

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marxveix wrote on 2026-01-11, 22:39:

You use what you have and if everything works as you like, why not.

Yeah, I guess that's true if you are just trying to build something with parts that you have. Just thinking that with DOS and Win9X, that the more devices you have in the system, the more chance there is of issues.

Reply 4 of 8, by wbahnassi

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My main goal is a very lean system. If the CMI8738 chip was sufficient, I could build the entire system without any expansion cards.. so the final build will be probably only 10-15cm thick, yet still capable and fully featured (has floppy drives, CD ROM).

But you are right that the board has ISA, so why not use a a single card that has both SB16 and real OPL3... well, I don't have one 😅 Plus the AWE64 had been the pinnacle of Creative's ISA sound cards, only crippled by CQM FM. Since I already have a great sounding FM chip on-board, well let's to put it to good use and fill the AWE64's weakness.

Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, Speedstar 24X, SB 1.5, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti

Reply 5 of 8, by RetroPCCupboard

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Ah, I get it now. Shame the onboard audio on its own wasn't sufficient. But your combination of AWE64 and onboard audio seems to be a good compromise

Reply 6 of 8, by RetroPCCupboard

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wbahnassi wrote on 2026-01-11, 21:48:

Having read people's experiences with CMI8738:

Cmedia CMI8738 - maybe its Biggest Secret

I wanted to listen to its OPL3 quality, and see how far can its SB16 part work with games.

I have just had a browse through that thread you linked. After initially sounding promising, it seems that it isn't going to be very compatible for digital audio. But FM does work, and sounds good. This was confirmed by your findings. That's a real shame.

Reply 7 of 8, by RetroPCCupboard

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As you know, if you have ISA slots, then there are better options than this anyway. But I wonder if your technique could be expanded for systems that are PCI only. There are PCI soundcards like SB Live and Aureal Vortex 2 that I think work ok with digital audio, but the FM sounds poor. Could they be paired with a CMI8738 card (or onboard audio)?

Reply 8 of 8, by wbahnassi

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It depends on how the PCI drivers operate.. As each driver uses a different technique for interception and rerouting, I imagine there needs to be some luck involved so the drivers can "stack up" without some bad interactions.
Worth giving it a shot though!

Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, Speedstar 24X, SB 1.5, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti

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