I think you need to set both A and B in the BIOS.

BIOS only lists options for Floppy A. Mobo for that system is an Intel D845PT.

If your BIOS only supports one floppy drive, then you are out of luck getting both drives to work at the same time.

Perhaps my question was misleading. I would like to use both but not at the same time. My understanding is that would be impossible anyway. Since there is only one interface at the back I expect I wouldn't be able to use both simultaneously. So I wouldn't be able to copy from one slot directly to the other.

As it is now I would have to copy from one slot to the hard drive. Open the case and swap the ribbon cable connection. Then copy from the hard drive to the other slot. What I hoped for was a way to switch between them without the part in bold.

These are two drives in one. Think of as the crossed part of the cable built into the device. You need a BIOS/Mainboard that supports both A and B floppy drives.

Yes, I think the others got it right - you need better bios support.

I have a similar drive, and no matter what cable/connectors, you'll have to be able to specify the existence of a drive B in the bios to make both slots work.

If you only are able to specify an 'A' in bios, then yes - which half of the combo is operationable at any time would most likely be a factor of where on the cable you connect it.

So you'd have to do the bold part every time you wanted to use a different drive size - as there would be no way for the mobo to know there was a second drive there.

You could of course buy an USB 3.5'' floppy drive - maybe that's a simpler solution than switching the mobo... you decide.... 😎
(but that would require an OS that recognizes such devices - XP/2000 or Vista most likely, not sure what you use/have installed)

I have Windows 98 installed on the system. It does support USB. I have a USB mouse attached to it, though I have to disconnect it and plug it back in to get the mouse to work when I first turn boot the system.

Edit: It just occurred to that a PCI add in card might have support for 2 floppy drives. There are several on ebay but I'm not sure what I should look for or if I would be able to find drivers for something like that.

I know there are PCI IDE cards out there.
And ISA floppy controllers(much less easy to find), but haven't seen any PCI variants.
Maybe you're mistaking the IDE cards for floppy controllers ?
Have any ebay links ?

As for win98, it got USB support, yes.
But... besides plugging in the odd mouse or printer, I've found it difficult to make it assign drive letters to drive like devices... 😒
(memory sticks, usb hdd's etc etc)
And if you're already having trouble with your mouse, weell...
Anyway, you would at least need some special win98 drivers for each USB gadget.