Forgot to add that when I enable the "Boot Up Floppy Seek" BIOS option, which I normally always leave disabled, I now get a "Floppy disk fail(40)" error. Pressing F1 and continue to boot it will give the same symptom as I described above. Normally that indicates no floppy drive or cable not connected correctly but that is not the case.

AFAIK it's the south bridge job, and it looks to be a BGA chip. Could be dying, could be cracked solder balls. Put the mobo on a flat surface and press the chip with your finger - see if that helps any. If there is a change in behaviour you need to reflow that BGA.

>Used multiple different floppy cables

that was my guess, try tracking floppy connector further and check continuity, maybe there is a crack somewhere along the way.

Deunan wrote on 2024-05-10, 17:08:

AFAIK it's the south bridge job, and it looks to be a BGA chip. Could be dying, could be cracked solder balls. Put the mobo on a flat surface and press the chip with your finger - see if that helps any. If there is a change in behaviour you need to reflow that BGA.

Just tried that but unfortunately that didn't change the behavior.

rasz_pl wrote on 2024-05-10, 17:29:

>Used multiple different floppy cables

that was my guess, try tracking floppy connector further and check continuity, maybe there is a crack somewhere along the way.

Going to do that tomorrow (if time permits). But had a good look already earlier when I did the repair work. So not to hopeful I will find anything new.

If BIOS shows floppy error only when seeking is enabled you can limit your search area quite a lot. All the BIOS does is step 43 times in and then out, checking the track 0 sensor output. This lets it detect 40-cylinder drives (360k). So the only signals used are drive select, motor on, direction, step and track 0 (that's input). Everything else doesn't matter.

BTW I never had it happen to me but it's possible for the floppy cables with twist to go bad at the twisted section (the cable is too thin and pressed to hard in factory, wires break inside). Try straight cable or the non-twisted connector and either set the drive to B: (if only to test) or there might be a drive letter swap option in BIOS.

Deunan wrote on 2024-05-11, 09:52:

If BIOS shows floppy error only when seeking is enabled you can limit your search area quite a lot. All the BIOS does is step 43 times in and then out, checking the track 0 sensor output. This lets it detect 40-cylinder drives (360k). So the only signals used are drive select, motor on, direction, step and track 0 (that's input). Everything else doesn't matter.

BTW I never had it happen to me but it's possible for the floppy cables with twist to go bad at the twisted section (the cable is too thin and pressed to hard in factory, wires break inside). Try straight cable or the non-twisted connector and either set the drive to B: (if only to test) or there might be a drive letter swap option in BIOS.

Found the issue. What I didn't test yet was to remove all cards (USB, network, sound cards). When I did that the floppy drive suddenly was working again. Then added them one by one and it seems the ISA sound card is causing this issue. Had to suspect this earlier as I had issues with sound suddenly not working when playing a game with an ALS100 card but thought it was a broken card. When replacing it with a ES1868F everything was working at first.

Sound card is still working correctly (with standard values IRQ5 A220 DMA1+DMA0). Only the floppy drive is not working anymore when the ES1868F card is inserted now. As the floppy drive is using IRQ6 and DMA2 there shouldn't be any resource conflicts.

So a bit puzzled at the moment. Anyone got an idea what could cause this? Will do a continuity/voltage test on the ISA slot tomorrow. But I have no idea how to measure the floppy connector on the motherboard though. So some hints (without oscilloscope) are appreciated.

Is this a sound card with extra IDE interface (for CD-ROM)? Is it disabled properly?

Deunan wrote on 2024-05-12, 15:32:

Is this a sound card with extra IDE interface (for CD-ROM)? Is it disabled properly?

Both the tested ASL100 and ES1868F have an extra IDE interface. I disabled them on both with their config tools.

Also just now measured the ISA connector and all voltages are within range. Also did a continuity test and so far everything seems ok.

*EDIT* Also added an ALS4000 PCI card (with IRQ5, DMA1, A220) and with that the floppy drive is also working. Didn't do a DOS sound test yet.

Forgot that I had a cheap oscilloscoop so took a look at the RDATA, MOTEA#, DRVSA pins on the floppy connector with and then without an ISA card. Unfortunately the signals are exactly the same. So I am out of ideas what the problem could be. So will be going with the ALS4000 PCI sound card for now. Not a bad DOS card at all but not what I had in mind.

So it doesn't work with either ISA card? But does work with PCI? Perhaps it's some sort of PnP issue, did you try manual assigment of the sound card IRQ/DMA to ISA in BIOS?
Or perhaps it's a some weird ISA slot problem, like maybe something got into one of the slots and is shorting DMA1 and DMA3 signals for example (or IRQ with either IRQ5 or IRQ7).

Deunan wrote on 2024-05-13, 13:10:

So it doesn't work with either ISA card? But does work with PCI? Perhaps it's some sort of PnP issue, did you try manual assigment of the sound card IRQ/DMA to ISA in BIOS?
Or perhaps it's a some weird ISA slot problem, like maybe something got into one of the slots and is shorting DMA1 and DMA3 signals for example (or IRQ with either IRQ5 or IRQ7).

I always do a manual reservation in the BIOS (if possible). Checked for shorts yesterday and took a good look as well. But no shorts are found. ISA socket is brand new and was soldered on the board as the motherboard lacks it normally. This mod has been done successfully before by other members on Vogons. I thought it was maybe a bad solder job but after intens investigation yesterday I can't find a problem. No shorts and voltage are in range.

Ah, so ISA slot was added later. I gave the photo another look, there's a few resistor packs near the ISA - are all of those populated on your mobo? I was wondering if there is perhaps a missing pull-up (or pull-down) for the IRQ or DRQ lines.
Another possibility is the BIOS, since it's not expecting to have ISA slot installed perhaps there are some internal chipset registers not set up correctly. This might be somehow affecting IRQ/DMA routing from the slot and the internally emulated floppy controller. It's a wild guess but I don't have other ideas.

Deunan wrote on 2024-05-13, 15:38:

Ah, so ISA slot was added later. I gave the photo another look, there's a few resistor packs near the ISA - are all of those populated on your mobo? I was wondering if there is perhaps a missing pull-up (or pull-down) for the IRQ or DRQ lines.
Another possibility is the BIOS, since it's not expecting to have ISA slot installed perhaps there are some internal chipset registers not set up correctly. This might be somehow affecting IRQ/DMA routing from the slot and the internally emulated floppy controller. It's a wild guess but I don't have other ideas.

It was working for a couple of weeks. So the BIOS supports it. Also other Vogons members used the standard BIOS.

I checked the motherboard before and all was there. But I didn't measure them so will do that in the future. For now I put it on the backlog as I am a little fed up with it. 😉

Yoghoo wrote on 2024-05-13, 16:57:

It was working for a couple of weeks. So the BIOS supports it. Also other Vogons members used the standard BIOS.

I checked the motherboard before and all was there. But I didn't measure them so will do that in the future. For now I put it on the backlog as I am a little fed up with it. 😉

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K7T Turbo2... and now my floppy isn't working. Coincidentally, I am also testing it with an ESS 1868F sound card.

This is quite puzzling, but I'm glad I'm not the only one experiencing it and I'm so glad you made this thread. I just finished putting the slot on the board maybe half an hour ago, and you've saved me a ton of time messing around trying to find the cause of the floppy problem.

By chance did you ever find a fix for this aside from just not using either an ISA sound card or a floppy drive?

If only my LS-120 drives hadn't all taken a poo and died at the same time a year or two ago... this would be a good candidate for one of those.

EDIT: This is so cool... I am testing the ESS sound card now and it works perfectly using Unisound. I didn't even have to touch the BIOS at all. The ISA slot just works. It's unfortunate that there seems to be a compatibility issue between sound cards and floppy drives for some reason.

I wonder if the problem is similar to the one in this thread?
Audician 32 conflicting with... floppy controller?

EDIT2: I just tried an SB16 CT2230 and the floppy is working perfectly. 🤷

Ozzuneoj wrote on 2026-02-05, 02:33:

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K […]
Show full quote

Yoghoo wrote on 2024-05-13, 16:57:

It was working for a couple of weeks. So the BIOS supports it. Also other Vogons members used the standard BIOS.

I checked the motherboard before and all was there. But I didn't measure them so will do that in the future. For now I put it on the backlog as I am a little fed up with it. 😉

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K7T Turbo2... and now my floppy isn't working. Coincidentally, I am also testing it with an ESS 1868F sound card.

This is quite puzzling, but I'm glad I'm not the only one experiencing it and I'm so glad you made this thread. I just finished putting the slot on the board maybe half an hour ago, and you've saved me a ton of time messing around trying to find the cause of the floppy problem.

By chance did you ever find a fix for this aside from just not using either an ISA sound card or a floppy drive?

If only my LS-120 drives hadn't all taken a poo and died at the same time a year or two ago... this would be a good candidate for one of those.

EDIT: This is so cool... I am testing the ESS sound card now and it works perfectly using Unisound. I didn't even have to touch the BIOS at all. The ISA slot just works. It's unfortunate that there seems to be a compatibility issue between sound cards and floppy drives for some reason.

I wonder if the problem is similar to the one in this thread?
Audician 32 conflicting with... floppy controller?

EDIT2: I just tried an SB16 CT2230 and the floppy is working perfectly. 🤷

I am using the floppy drive but I forgot what sound card I am using atm. I'm on holiday so can't check it now. Will check it out next week when I'm back.

Ozzuneoj wrote on 2026-02-05, 02:33:

Yoghoo wrote on 2024-05-13, 16:57:

It was working for a couple of weeks. So the BIOS supports it. Also other Vogons members used the standard BIOS.

I checked the motherboard before and all was there. But I didn't measure them so will do that in the future. For now I put it on the backlog as I am a little fed up with it. 😉

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K7T Turbo2... and now my floppy isn't working. Coincidentally, I am also testing it with an ESS 1868F sound card.

This is quite puzzling, but I'm glad I'm not the only one experiencing it and I'm so glad you made this thread. I just finished putting the slot on the board maybe half an hour ago, and you've saved me a ton of time messing around trying to find the cause of the floppy problem.

floppy controller is DMA, ISA cards screwing with DMA might be BALE issue.
Re: Xi 8088 by Segey Kiselev
"In my case, the graphics card seemed to respond to the ALE signal during a DMA transfer, placing data on the bus at the same time the RAM was supplying audio sample data to the sound card. "

Yoghoo wrote on 2026-02-05, 06:39:

Ozzuneoj wrote on 2026-02-05, 02:33:

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K […]
Show full quote

Yoghoo wrote on 2024-05-13, 16:57:

It was working for a couple of weeks. So the BIOS supports it. Also other Vogons members used the standard BIOS.

I checked the motherboard before and all was there. But I didn't measure them so will do that in the future. For now I put it on the backlog as I am a little fed up with it. 😉

Oh boy. I just spent a couple hours replacing a bunch of caps, pulling an ISA slot off of a dead board and installing it on my K7T Turbo2... and now my floppy isn't working. Coincidentally, I am also testing it with an ESS 1868F sound card.

This is quite puzzling, but I'm glad I'm not the only one experiencing it and I'm so glad you made this thread. I just finished putting the slot on the board maybe half an hour ago, and you've saved me a ton of time messing around trying to find the cause of the floppy problem.

By chance did you ever find a fix for this aside from just not using either an ISA sound card or a floppy drive?

If only my LS-120 drives hadn't all taken a poo and died at the same time a year or two ago... this would be a good candidate for one of those.

EDIT: This is so cool... I am testing the ESS sound card now and it works perfectly using Unisound. I didn't even have to touch the BIOS at all. The ISA slot just works. It's unfortunate that there seems to be a compatibility issue between sound cards and floppy drives for some reason.

I wonder if the problem is similar to the one in this thread?
Audician 32 conflicting with... floppy controller?

EDIT2: I just tried an SB16 CT2230 and the floppy is working perfectly. 🤷

I am using the floppy drive but I forgot what sound card I am using atm. I'm on holiday so can't check it now. Will check it out next week when I'm back.

Just checked and I am only using a PCI sound card atm (Sound Blaster Audigy 2 ZS). I now remember I installed Windows ME on this pc so I didn't need an ISA sound card in the end.

rasz_pl wrote on 2026-02-05, 07:18:

floppy controller is DMA, ISA cards screwing with DMA might be BALE issue.
Re: Xi 8088 by Segey Kiselev
"In my case, the graphics card seemed to respond to the ALE signal during a DMA transfer, placing data on the bus at the same time the RAM was supplying audio sample data to the sound card. "

Could indeed be the case. Don't have an installed ISA card on this motherboard so can't test the following at the moment but got some AI snippets which could help:

1@echo off
2echo --- VIA 686B ISA/Floppy Conflict Fix ---
3echo Target: VIA ISA Bridge at 0:7.0
4echo.
5
6echo [Step 1] Disabling ISA Post Write (Reg 52h)...
7pciedit -w 0:7.0 52=FE
8
9echo [Step 2] Sharpening ALE Pulse (Reg 54h)...
10pciedit -w 0:7.0 54=02
11
12echo [Step 3] Boosting ISA/DMA Priority (Reg 48h)...
13pciedit -w 0:7.0 48=01
14
15echo [Step 4] Enabling PCI Delayed Transaction (Reg 70h)...
16pciedit -w 0:7.0 70=02
17
18echo.
19echo --- Verification (Should match: FE, 02, 01, 02) ---
20pciedit -r 0:7.0 52
21pciedit -r 0:7.0 54
22pciedit -r 0:7.0 48
23pciedit -r 0:7.0 70
24echo.
25echo Test your Floppy Drive now.

I would test it one statement at the time and not all at once btw. Values can be adjusted from the examples above.

Just put it here as a reminder to test it later. Use it at your own risk. 😀 It could lockup your system or cause data corruption.

Yoghoo wrote on 2026-02-11, 18:27:

Could indeed be the case. Don't have an installed ISA card on this motherboard so can't test the following at the moment but got […]
Show full quote

rasz_pl wrote on 2026-02-05, 07:18:

floppy controller is DMA, ISA cards screwing with DMA might be BALE issue.
Re: Xi 8088 by Segey Kiselev
"In my case, the graphics card seemed to respond to the ALE signal during a DMA transfer, placing data on the bus at the same time the RAM was supplying audio sample data to the sound card. "

Could indeed be the case. Don't have an installed ISA card on this motherboard so can't test the following at the moment but got some AI snippets which could help:

Copy code to clipboard

1@echo off
2echo --- VIA 686B ISA/Floppy Conflict Fix ---
3echo Target: VIA ISA Bridge at 0:7.0
4echo.
5
6echo [Step 1] Disabling ISA Post Write (Reg 52h)...
7pciedit -w 0:7.0 52=FE
8
9echo [Step 2] Sharpening ALE Pulse (Reg 54h)...
10pciedit -w 0:7.0 54=02
11
12echo [Step 3] Boosting ISA/DMA Priority (Reg 48h)...
13pciedit -w 0:7.0 48=01
14
15echo [Step 4] Enabling PCI Delayed Transaction (Reg 70h)...
16pciedit -w 0:7.0 70=02
17
18echo.
19echo --- Verification (Should match: FE, 02, 01, 02) ---
20pciedit -r 0:7.0 52
21pciedit -r 0:7.0 54
22pciedit -r 0:7.0 48
23pciedit -r 0:7.0 70
24echo.
25echo Test your Floppy Drive now.

I would test it one statement at the time and not all at once btw. Values can be adjusted from the examples above.

Just put it here as a reminder to test it later. Use it at your own risk. 😀 It could lockup your system or cause data corruption.

This is interesting... I feel like this would be helpful to diagnose the source of the problem rather than to fix it completely though, since the floppy is already not working properly before even booting the OS. So, you'd have to disable boot-up floppy seek probably to avoid errors (mine has them at times with the ESS card installed), and you would probably not be able to boot from floppy at all.

I will see if I can run this since I still have the board handy. I'm curious. 😀