You may want to check this thread Floppy 3 & 4 without BIOS support

I read, you wrote that driver. I'm a bit confused, due to discussions in the german dosreloaded forum on this topic.
So, only if I'm able to disable the onboard-controller on my SR440BX board in the up-to-date P10 BIOS, I can make use of the FDC-BIOS in the adaptec AHA-1542CF? Or is it also possible to use the NEC driven controller of that board for let's say the a: drive and the Adaptec FDC for the B: and say D: drive? I recently saw software that supports up to 4 floppy drives. Will the adaptec support 4 drives itself?

Is this driver similar or compareable to a BIOS-Extension in it's sort of functionallity like a DDO diskmanager BIOS-Extension for int 13? I mean regarding the time of access? So can one boot from such a adaptec connected FDD?

No, the adaptec drive will not support 4 drives. If you disable your onboard controller, Adaptec card can natively (without any drivers) support two floppy drives and they will be bootable. If the onboard controller is enabled you can configure the Adaptec card to use alternative floppy port address(370) and add two floppy drives. But you'll need the driver mentioned in that thread for that.

Thank you for your kind support, and of course for writing such drivers! I'll then buy such a card.

Iarsin wrote on 2021-12-02, 13:27:

Thank you for your kind support, and of course for writing such drivers! I'll then buy such a card.

It was actually maxtherabbit, who wrote the driver 😀
BTW if all you need is two FDDs you don't need an Adaptec card. A plain inexpensive FDD controller, like Goldstar Prime, would do.

No, I don't think so? Because the mobo BIOS only supports the configuration and connection of a single floppy drive? But maybe it'll work nevertheless with that mentioned driver? Sorry, still a bit confused ...

Yes, you're right if the mobo BIOS suppors only one FDD then it won't do.

If you can completely disable the onboard floppy controller, you could then add any 8-bit floppy controller to the ISA slot. There is no such thing as a 16-bit floppy controller, the 16-bit cards you see that contain floppy interfaces are only 16-bit because they also contain IDE interfaces.

If you were to add a generic/basic/ whatever 2 drive FDC to your ISA slot, you could use the motherboard BIOS to support the A drive, and my driver to support the B drive. If you are dead set on supporting a total of 3 or 4 drives, it would be better to just purchase a 4 drive controller, like sergey's

Ah, okay. Thank you maxtherabbit, also for the driver. As a maximum I would like to attach two 5.25" (360k and HD) and a maybe 2.88MB 3.5", three in total to the SR44ßBX. Maybe only two drives, but more than the supported single drive.