Does your board really has a notch which prevent you from installing 5V cards? It's pretty uncommon.
As far as I know - no, chip is only 5v.

Yes, the slot on the board has the tab that blocks 5V only cards.

The PCI YMF7xx chips themselves are 3.3V devices and have no issues with 3.3V only power. I think I have seen at least one card made with dual notches.

Somebody has a few YMF724 based cards for sale on eBay that will work in 3.3v and 5v PCI slots:

https://www.ebay.com/itm/Yamaha-724-XG-YMF724 … 24/254017434013

cyclone3d wrote:

Somebody has a few YMF724 based cards for sale on eBay that will work in 3.3v and 5v PCI slots:

https://www.ebay.com/itm/Yamaha-724-XG-YMF724 … 24/254017434013

Has anybody had prior experience with Super Grace products? I have never heard of them before.

A lot has happened since I last posted. I purchased that "SuperGrace" YMF724F-V sound card with the 3.3V notch, and it didn't work, most likely because the YMF724 requires a digital 3.3V supply but 5V for I/O.

I looked at the datasheet for the YMF744, and lo and behold, it supports 3.3V for both supply and I/O. I kept looking for boards with the 3.3V notch, but didn't find any. Then I read about this daring person who cut the 3.3V notch into a different PCI card to put it in a 3.3V-only PCI slot, and it worked there.

So I figured, it's worth a shot. I bought an AOpen AW744L-II new-old stock off eBay and used my dremel to cut out the notch. And guess what?

Yeah, it still doesn't work. Unlike the SuperGrace card, which just wouldn't initialize properly, putting this notched card into my board bizarrely breaks the Primary master IDE device (not the slave) and the PS/2 mouse for some reason, in addition to freezing Windows 98 when it tries to install the device. I'm really confused as to how and why that happens.

Looking at the board, it has a Sigmatel STAC9708T codec, which naturally requires a 5V analog supply. Didn't notice that before. The otherwise identical Sigmatel STAC9711 codec is the one which takes a 3.3V analog supply. It's not clear to me how that would cause all of the weirdness on the PCI bus that's causing my computer to freak out.

So close, yet so far. The codec is a SMT device, so it's theoretically possible to swap it out for its 3.3V cousin, but the pins are very fine pitch and I would have to get a soldering expert's help with that, assuming I can even source the IC.

All that said, does anyone else have any other ideas why this AOpen board is causing my system to misbehave?

Have you completely ruled out resource conflicts? I would disable everything that isn't completely necessary in the BIOS, try playing with resource allocation settings if there are any, use the "reset configuration data" option after disabling any unnecessary components (again if that option exists in your BIOS).

What is the model of your motherboard?

The motherboard is a PCEngines alix1e.

What about pulling the 5v power from the power supply? Just need to get a few points to solder to that the pins originally went to.

Actually.. look at pins B12 and B13. Those two are supposed to be ground for a 5v card as seen here:
https://pinouts.ru/Slots/PCI_pinout.shtml

If I remember right though, the ground plane for that card has the ground plane hooked to all of the different ground pins.

What you would really need to do is mask off all the power pins and then feed 5v from the power supply to the card in order to get it to work properly.. if in fact, it will not work with 3.3v.

Looks like these pins would have to be switched from 3.3v to 5v:
A10
A16
A59

Pinout is here:
https://pinouts.ru/Slots/PCI_pinout.shtml

I could always try modding one of my cards to see what it takes to get it working in a 3.3v slot. Might actually help me sell more cards.

Is it safe to mod a 5v only card to work in a 3.3v slot? I wouldn't want to fry a motherboard.

Not even sure if I have a 3.3v only PCI motherboard.

Edit: I could always just mod one of my PCI riser cables for testing purposes.

Is it safe to mod a 5v only card to work in a 3.3v slot? I wouldn't want to fry a motherboard.

I can tell you that the alix1e's manual cautions against it. If you actually put 5V onto any pin that's expecting 3.3V, then yes, damage is likely. Supplying 5V to the card independently from the PCI slot is bound to lead to some 5V I/O and then magic smoke coming out.

That said, if there's no 5V supply feeding the card, and no power circuitry on the card capable of generating 5V, then there's no way the card could put 5V on the bus.

In all of my searches, I have not been able to find a single YMF744 or YMF754 card with the 3.3V notch. There are Aureal Vortex and Vortex2 cards with the notch, and some SB Live! OEM boards with the 3.3V notch, but those are inferior for DOS gaming to the Yamaha XG.