maxtherabbit wrote on 2025-05-17, 17:33:

I've heard there is one from Sergey but I have no experience with it.

This is Sergey's project, I also have no experience with it but it seems like it covers anything one could ever need.
https://github.com/skiselev/monster-fdc

The actual firmware is here:
https://github.com/skiselev/floppy_bios

And now I remember why I didn't try it before, it expects to be installed on an EEPROM to save its configuration back to itself. Although the docs do describe how to hard code the values yourself before programming

You'll have to confirm that your floppy controller hardware supports 4 drives correctly.

When they made the PC, IBM decided that changing drive jumpers was too complicated for the average
buyer, and they didn't want to stock two drives differing only in jumper settings ( A: and B: )
They also expected to run from floppy in many cases (the 5150 didn't have a hard drive), so they wanted to
not be running all drive motors all the time (the interface has only 1 "motor-on" signal)

So they came up with the wanky twisted cable between drive A: and drive B: which makes select A: appear at B: for physical
drive A: and brought motor-on for A: to a different signal.

This means the "standard" C: and D: selects are not in the right places on the IBM FDC board connector (and most mainboards
made since) and in many systems are simply not hooked up at all...

DaveDDS wrote on 2025-05-17, 19:45:

You'll have to confirpcm that your floppy controller hardware supports 4 drives correctly.

No problem there, I'm currently using the WONDER34 installable device driver (as recommended by Chuck G) to operate all 4 drives in DOS, and they work a treat with IMD /4 too 😀

So can anyone chime in with some hands on experience with Sergey's firmware?

I'm also interested how I can access floppys from a secondary FDD controller like on an Adaptec 1522.

Disruptor wrote on 2025-05-17, 21:37:

I'm also interested how I can access floppys from a secondary FDD controller like on an Adaptec 1522.

Sergey firmware purports to support drives on both primary and secondary FDC

The quad floppy controller I had
1. Had its own bios
2. Had 2 separate cables

I did own a non-standard Innovion pgs3 graphics system and the 3.5” floppy in that had a massive number of jumpers for all sorts of different drive select / ID# crapola I have never seen in a pc.

The only time I’ve seen a floppy cable with 3 connectors was in a system with dual floppies but the tape drive was on the same cable, never understood how that worked.

Yes every "IBM" style 4 floppy controller is going to have two separate cable attachments. Internal and/or external. One header will have drives 0/1 wired and the other will have drives 2/3 wired

Well I broke down and setup an EEPROM to test out Sergey's floppy BIOS. So far it seems perfect. I'm not shadowing it and performance is good. It is able to handle drives on both primary and secondary FDC simultaneously and lets you define them in any logical order irrespective of the physical drive selects. Pretty cool

OK I found one issue with it - floppy file operations no longer work in windows 3.11. This could be attributable to my using 32-bit disk access for the hard drive.

Windows works fine otherwise, and will even display the directory of any floppy drive, but it crashes when you try to copy a file from diskette to the hard drive.

I was able to solve the windows 3.11 issue. All I had to do is define a 4th drive in the multi floppy BIOS and now it Just Works. The drive doesn't even have to be physically present.