Sometimes PCI SATA cards appear as SCSI devices - does your BIOS have an option to enable booting from SCSI, or to enable/disable SCSI ROM BIOS extensions?

I agree. I just looked at the manual for your board, and it looks like you should set the first boot device (or later if you want the option to boot from a removable drive first) to "SCSI" in the "Advanced BIOS Features" menu.

It doesn't look like the BIOS has any other settings for Option ROMs.

BTW, some SiI3112 cards don't have a bootable ROM. I have two cards with the chip, and one of them will not boot from attached drives.

To make matters worse, a lot of those same cards don't have an EPROM you could flash with a bootable BIOS.

If you are using something that is AT hardware compatible, like a generic ISA or VLB IDE controller, you configure the drives in the motherboard BIOS because the motherboard BIOS is going to manage the device.

If you are using an add-in HD controller that isn't a hardware compatible AT drive controller, like just about all PCI cards & ISA SCSI cards, you won't configure the drives in the motherboard BIOS because the motherboard BIOS won't know anything about the controller. You would set the Motherboard BIOS to no drives and let the BIOS on the controller card manage the storage devices.

What do you do if you don't have an option ROM on the card? Well you are not going to boot from it very easily and you can't even access the drives until you load storage drivers, either in DOS or windows. I once bought this 486 motherboard with a built in SCSI controller to be a Netware server. Seems like it was going to be awesome. Turns out the Motherboard BIOS didn't know anything about the SCSI controller. Had to add an IDE drive to get the thing to boot. Worked fine I suppose after that, I guess, but it was messy. Seemed like a giant server at the time. It had a 1GB SCSI drive in it.

Here are two PCI cards, one with an option ROM, the other without.

I suppose if you got a copy of the BIOS for the card, you could burn it to a chip and stick it in another card that has an option rom socket, like most network cards do. Might work.