After replacing the UM8663BF IC, the onboard floppy controller remains non-functional. However, in my case, the BIOS still shows A:\ as 1.44MB 3 1/4" floppy drive. Anyway, I am left wondering which component, IC, or connection is causing this problem. The worst case scenerio would be something wrong with the southbridge chipset, which communicates with the Super I/O (UM8663).
I remember when the floppy controller on this MB suddenly died. I had the system on 24/7 with a 5 month uptime. There was no obvious sign of trouble until an NT4 BSOD message appeared. After that, the floppy controller didn't work. This happened more than 5 years ago.
There is a workaround for this problem, it is to use an ISA I/O card, preferably one with the same UM8663 Super I/O chips. On the ISA I/O card, I disable all features except for the floppy controller (via jumpers). In the motherboard's BIOS, it is important to leave the onboard FDC set to enabled and A:\ to 1.44 MB, 3 1/4" drive, and to ensure floppy seek at boot is disabled. Then connect your floppy drive to the ISA card's floppy header. It should work fine. It is still ugly to have to use an extra ISA card for this though. I would prefer to find the source of the problem.
I have some 4DPS motherboards which also cannot read from the floppy drive via the onboard floppy controller. I have spare Winbond Super I/O chips for these boards, but I am afraid that replacing them might be fruitless inlight of my recent findings. Anyone have any ideas where to start tackling this problem?