I've just realized that some motherboard don't support more than two floppy drives. And yet the manual seems to say otherwise...

My MSI 865PE Neo2-S does support two floppy drives, my Intel D865PCD supports just one.
What does your bios say ?

The BIOS allows to swap units, so I presume it does support two drives. Why this isn't working on my board is a mystery.

> 1 floppy port supports 2 FDDs with 360K, 720K, 1.2M, 1.44M and 2.88Mbytes

What else could be wrong?

If the Sony is at the end after the twist in cable and the Chinon is in middle before twist: make sure the Chinon J1 jumpered for DS1 (#3) and the Term jumper (#1) is removed....
some boards do not like the Term enabled if in middle of cable....the Sony should be fixed termination and must be at cable end iirc.

@Horun: I lost you at

> make sure the Chinon J1 jumpered for DS1 (#3) and the Term jumper (#1) is removed....

I'll check. Hopefully this doesn't require soldering? Also, this same configuration worked on a motherboard with SiS chipset.

Here's the current jumper configuration:

TM is the Term jumper, pull it off and try again. With the 3.5" on the end and 5.25" in middle of cable.
Thanks for the picture, could not find one of the jumpers...

Tried: it didn't work. 🙁 I suspect it's the motherboard.

Theletterf wrote on 2025-03-02, 15:40:

The FDD ribbon cable has both standard and EDGE connectors for units A and B. When I plug either the Sony or the Chinon as A, leaving the other unit out, they both react well to POST tests and floppy seek. When I try plug one of the drives as B, they aren't detected and the infamous error 40 appears. No lights, no sounds, nothing. This cable, and the units, previously worked when plugged to a different motherboard.

This might be a silly question but does the cable have a partial twist at the end for the other connector? It could be a single-drive cable without a twist, just with 2 connector types. Post a photo if in doubt.

Alas, it's four connectors in total for the same cable. Plugged on the other board and it works.

No lights and no head movement is an odd behaviour if the drives work on another mobo. What do you mean by "The BIOS allows to swap units, so I presume it does support two drives."? Usually if there is such an option, there also needs to be two separate config options for drives A and B. Do you have two separate options or just one?

I have two as well. At this point, I think the BIOS doesn't know that the mobo can't handle two floppy drives.

It's possible but that can be tested. Connect only one floppy drive but to the B connector (before twist). Set it up in BIOS as B but enable the floppy swap option. This should result in one working drive as A: in the OS. Does it work that way? If not try setting it up as A: (still on B connector though) since the swap option might be implemented differently.

If you can't get the B connector to work with these tries then perhaps yes, there are some signals on the mobo floppy connector that are not present. That would mean the mobo only supports one floppy even if BIOS has options for two. But if it does work, or at least looks like it's doing something, then perhaps the mobo doesn't like the drive termination packs for some reason.

Theletterf wrote on 2025-03-02, 18:46:

The BIOS allows to swap units, so I presume it does support two drives. Why this isn't working on my board is a mystery.

Sometimes BIOS doesn't get updated when it doesn't have to be... Setting B: drive to NONE
works just fine with only one drive...

Plus, "swap floppy" would have limited use with only one drive supported - if for some reason you
want only a B: drive (and no A:) this would do the trick!

And I can't really think of another reason for "swap floppy"! You can accomplish this by just swapping the
connectors - so the only real reason to "swap floppy" would be if you have different connectors (eg: only
5.25 on A: and 3 on B:) and wanted the other type as A: - or if the cable doesn't reach the place where
you want B: - both seem pretty unlikely/uncommon.. I'd guess the mainboard doesn't support two drives.
(If you can look closely at the floppy connector on the mainboard and see if there's anything connected to
the B: select)

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

And keep in mind that if the manufacturer makes two boards similar enough to work with the
same BIOS (maybe one has floppies, one has only one) - It's less work to inventory and keep
stocks of only one part than it is for two - a good reason the BIOS might both support two
drives and allow them to be swapped!

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

There have been known cases of motherboards saying they support 2 floppies (and possibly even having a contemporary supporting onboard chip), and fail to support 2 floppies. Floppy support really went downhill in the 2000's. Even if your BIOS seems to indicate support, it might not work. I guess this points directly to the board design.

The reason I ever use "floppy swap" is to boot from 5.25 instead of the 3.5. Booting from floppy is part of my tests when cleaning/repairing a drive to verify function.

I had a board like that once, wish I could remember the model, but it had only one option for floppy, drive A: and "swap floppies" in the "advanced" menu. On a board like that, you'd be changing the drive letter and possibly stopping it's ability to boot from the floppy, since most computers (especially a "newer" one) boot from A: only.

I'd be curious to know if "swap floppy" actually swaps with ImageDisk?

ImageDisk talks to the FDC directly, completely bypassing DOS and BIOS.

If "Swap floppy" doesn't swap for ImageDisk, that's what I'd expect, and means it's
only swapping within BIOS calls and is always accessing physical drive A:

If "swap floppy" does swap for ImageDIsk, it means there has been an hardware
change and drive A: is now on the B: select .. that would mean extra hardware on the
mainboard (that most would never use - so why add the expense?).

-or- The system chip with the FDC integrated supports swapping the selects.
Which seems "odd" only one drive is supported, but you never know... The FDC
could support only one drive and allow it to be either A: or B:, it could support
two drives and B: is just not connected on that revision of the mainboard.
-or it could be that some random designer was having a good/bad day and just
decided it should be a thing -

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

Major Jackyl wrote on 2025-03-05, 22:49:

The reason I ever use "floppy swap" is to boot from 5.25 instead of the 3.5. Booting from floppy is part of my tests when cleaning/repairing a drive to verify function.

Do you have a cable with only 3" connector at the end (A:).

I think all of my floppy cables have both 5.25" and 3" connectors at both A: and B: positions.
Sounds like the type of cable you should have if you are often cleaning/repairing drives.
(if you are changing/plugging in the drive anyway - why not just plug it into appropriate connector
and have one less BIOS setting to track is correct)

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