I'm hoping someone might have an idea or two to try, as I'm at my wits end getting a 3.5 floppy drive to work on my 386 build.

Motherboard is a UMC of somekind. Not sure on the specific model but has UM82C491F / 9480S / RM0308 written on the board (see photo attached).

The system seems to detect that a floppy drive is there (and if not there, it will give an error) and makes that noise on boot, but I am unable to boot from any disk nor is DOS able to read anything - "General failure reading Drive A". Attempting to format a disk also fails.

I have tried 3 different drives, 3 sets of cables (in all possible ways) and 3 different controller cards (all from the 90s, so surely wouldn't be stuck reading only 720KB disks?). The drives and cables are verified as working on other machines. I've double checked the right kind of floppy drive is selected in the BIOS.

I have no issue with IDE drives on this machine using the same controller cards I've tried the floppy drives on. They are detected and boot up just fine. I also have a CD-ROM as a slave on the same IDE channel as the hard drive, and it too works flawlessly. No jumpers on the cards to configure.

I've tried removing everything except the controller card and video card to rule out resource conflicts or weird conflicts with any other cards. No dice.

Anything else I might attempt? Getting quite stumped.