You've tried different drives, to be sure, have you tried different cable(s) as well? Does the drive's light come on at all during the POST? During the POST, does it act differently with the drive connected versus with the drive disconnected?

The floppy controller is a part of the ITE chip. Floppy pins are 51..65 (top half of the right side of the chip), the traces for those are going under the battery.

Check the cable and power-supply as well.
Also confirm that the drive you are trying to use is currently jumpered
as drive 2 (on a PC - with the twisted cable, both drives must be
configured as drive 2 (NOT 1) and the actual select position is determined
by the position on the cable).

When you say "not recognized", does it mean the system thinks there is no
floppy drive - or it see's it but can't read/write it.

If the former, checked that the floppy is configured correctly in BIOS.

I see a BIOS battery on the board - any chance that it's dying and the
BIOS is loosing it's configuration. (usually the BIOS will detect this
and let you know - but all kinds of strange strange stuff has made it into
PC designs - so I'd check just in case).

Does the drive activate during POST - usually BIOS will inventory drives.

If these are true, on the off-chance that there's something misconfigured
in the OS - I set the BIOS to boot floppy first, and try booting a DOS floppy.

Does it recognize a drive configured as B:?

If the latter, does the drive activate when you try and access it.

If no, there's something fundamentally wrong, I would confirm that it's
configured correctly in BIOS, possibly a jumper setting somewhere...

If yes, and you've verified drive/cables/power, chances are your FDC has
failed - I'd have to see a schematic, perhaps there are a few external
components that could fail, but most likely the failure would be in one
of the "system chips" which would be very hard to replace.

In developing ImageDisk, I sometimes wanted better floppy controllers than were
built into a mainboard. I would sometimes use a FDC on a card (often a SCSI
hard drive interface with build in FDC - just ignore the SCSI part)
Depending on how your BIOS lets you configure the floppy disk
system, you might be able to do something like than...

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

I did more tests with the floppy drive connecting it in both ways, as disk A and as disk B. Also changing some settings in the BIOS.

By plugging the floppy drive into the connector on the end of the cable and using the following BIOS settings:

STANDARD CMOS SETUP
.
.
* Floppy Drive A: 1.44 MB 3½
* Floppy Drive B: Not Installed
.
.
ADVANCED SETUP
.
.
* 1st Boot Device Floppy
* 2nd Boot Device IDE-0
* Floppy Drive Swap Disabled
.
.
FEATURES SETUP
.
.
* OnBoard FDC Enabled
.
.

I found that with this setting I can boot from a floppy disk and drive A is accessible in MS-DOS. If I boot from the hard drive, drive A is not accessible in MS-DOS and if I try to access Drive A which is shown as 5¼ in Windows 98, the computer stops responding.

By plugging the floppy drive into the middle connector on the cable and using the following BIOS settings:

STANDARD CMOS SETUP
.
.
* Floppy Drive A: Not Installed
* Floppy Drive B: 1.44 MB 3½
.
.

ADVANCED SETUP
.
.
* 1st Boot Device Floppy
* 2nd Boot Device IDE-0
* Floppy Drive Swap Enabled
.
.

FEATURES SETUP
.
.
* OnBoard FDC Enabled
.
.

With this configuration I can boot from a floppy disk and drive A is accessible in MS-DOS.
If I boot from the hard drive, the floppy drive is accessible from drive B in MS-DOS, in Windows 98 it was accessible up to a certain point from drive A and worked correctly, but for some reason I don't understand now it shows up as a 5¼ disk A and if I try to access it, the computer stops responding, also I noticed that the item GENERIC NEC FLOPPY DISK does not appear in the Disk drives menu of the device manager.

* I also tried with a new CR2032 battery and it made no difference to the results.
* Without connecting any floppy drive to the board and keeping the default settings, drive A is not accessible in MS-DOS, and in Windows 98 it shows as A 5¼, and freezes the PC if I try to access it.

Is it possible that the fault is due to a defective capacitor related to the BIOS?

vico wrote on 2024-12-09, 21:18:

With this configuration I can boot from a floppy disk and drive A is accessible in MS-DOS. If I boot from the hard drive, the fl […]
Show full quote

With this configuration I can boot from a floppy disk and drive A is accessible in MS-DOS.
If I boot from the hard drive, the floppy drive is accessible from drive B in MS-DOS, in Windows 98 it was accessible up to a certain point from drive A and worked correctly, but for some reason I don't understand now it shows up as a 5¼ disk A and if I try to access it, the computer stops responding, also I noticed that the item GENERIC NEC FLOPPY DISK does not appear in the Disk drives menu of the device manager.

* I also tried with a new CR2032 battery and it made no difference to the results.
* Without connecting any floppy drive to the board and keeping the default settings, drive A is not accessible in MS-DOS, and in Windows 98 it shows as A 5¼, and freezes the PC if I try to access it.

Is it possible that the fault is due to a defective capacitor related to the BIOS?

It does seems like your BIOS is losing it's settings...

If you set it up so that it boots/works (for a few times)...
After it messes up - if you go back into BIOS setup, are the settings
still correct?

If no, try setting them correctly, then try booting from hard-drive and never accessing floppy...
(you could perhaps disconnect floppy to prevent BIOS from doing any more that detect - but
this might cause BIOS to change it to "None")
Do they still get messed up - if yes, try setting correctly, then power-off (don't boot), and wait
say twice as long as it normally takes for them to mess up --- Then power-on and without booting
go to BIOS setup .. see if they messed up.

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

DaveDDS wrote on 2024-12-09, 21:55:

It does seems like your BIOS is losing it's settings... […]
Show full quote

vico wrote on 2024-12-09, 21:18:

With this configuration I can boot from a floppy disk and drive A is accessible in MS-DOS. If I boot from the hard drive, the fl […]
Show full quote

With this configuration I can boot from a floppy disk and drive A is accessible in MS-DOS.
If I boot from the hard drive, the floppy drive is accessible from drive B in MS-DOS, in Windows 98 it was accessible up to a certain point from drive A and worked correctly, but for some reason I don't understand now it shows up as a 5¼ disk A and if I try to access it, the computer stops responding, also I noticed that the item GENERIC NEC FLOPPY DISK does not appear in the Disk drives menu of the device manager.

* I also tried with a new CR2032 battery and it made no difference to the results.
* Without connecting any floppy drive to the board and keeping the default settings, drive A is not accessible in MS-DOS, and in Windows 98 it shows as A 5¼, and freezes the PC if I try to access it.

Is it possible that the fault is due to a defective capacitor related to the BIOS?

It does seems like your BIOS is losing it's settings...

If you set it up so that it boots/works (for a few times)...
After it messes up - if you go back into BIOS setup, are the settings
still correct?

If no, try setting them correctly, then try booting from hard-drive and never accessing floppy...
(you could perhaps disconnect floppy to prevent BIOS from doing any more that detect - but
this might cause BIOS to change it to "None")
Do they still get messed up - if yes, try setting correctly, then power-off (don't boot), and wait
say twice as long as it normally takes for them to mess up --- Then power-on and without booting
go to BIOS setup .. see if they messed up.

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

The BIOS settings are being maintained, but it seems that MS-DOS and Windows 98 are not correctly recognizing these settings, so I suspected that the CMOS is not being read correctly due to a power failure related to a capacitor or other defective component.

I discovered that this was not a hardware issue, but due to a corrupted MBR. When cloning the contents of one disk to another, the boot configuration is also cloned, however this boot configuration is incorrect, or prone to corruption. I reinstalled XOSL 1.1.5 and reconfigured the boot from scratch and the floppy issue no longer occurs.
I thought it was important to make this clarification, thank you all for your help and patience.