Can you make a backup of the current bios ? I have boards with AMI bios, so yours interest me ^^

I'm not sure the Ami bios lets you do that though. Have you tried a piece of software called "boot_b" ?

Put a mechanical switch to swap the A and B drive post and just boot.
Quite some BIOSes were able to boot, no matter which kind of drive was installed.

Put another twist in the cable between the controller and the 3.5" drive.

i think it's easier to just swap the bios instead of disassembling cables ^^

i'll try to backup the bios, perhaps i got time today. What exact eproms are used? i got some 512k 256k, 1mbit etc.

I have an Amibios...so neee an award

Just modify the cable.

What I would do is pull the B: connector off, add a twist in the cable before where it went, and put a new connector on. It sounds like your middle connector is the 3.5" drive, so you just need an IDC 34-pin female connector. You can get those from Digikey or Ebay or wherever.

I like to use (e.g.) Wurth pn# 61203423021 because they're pretty easy to stick on the cable, they stay put once installed, and have an optional cable strain relief you can pop onto the top. I usually use my finger nail to push a few conductors through the IDC, then put the housing together and use a pair of pliers with a wide jaw and flat ends to compress the connector on. Use some paper towels or a cloth to prevent marring the surface too much (though a little is normal and won't hurt anything). Alternatively, you can actually install these completely by hand, it just takes a while.

Voila. A cable with the connectors you need where you need them. FYI, I've had pretty good luck re-using the card-edge connectors for 5.25" drives, but the 3.5" connectors tend to lose their pins when you take them apart. I consider those single-use. Luckily, they're easy to source.

One other option could be:
Install e.g. a network card carrying an XTIDE Bios Extension EPROM. It allows you to swap drives on boot.

there's also some VGACOPY method. I'll modify the cable if i can't find one with another twist

Also, you can use a floppy ribbon extension cable for your 3.5" drive.

I just ordered some really long floppy cables from ebay. I just didn't see the point of doing anything more complicated.

Aw, you're missing out! Until you start making your own, you just don't know the joys of right-length cables, with the conductors sliced into groups of 8 or so and zip-tied into a "rounded" cable. It makes cable management so.. SO.. much easier. 😀

I like Baby AT or micro ATX cases, and tend to stuff a lot of hardware in them. My 486 and Pentium builds each have ribbon cables to the floppy, IDE HDD, separate IDE channel for the CD-ROM, and SCSI to a ZIP drive. Despite all of that, it's neat and tidy, and I can actually see the CPU fans without the PC's entrails spewing out everywhere. 😁

i did that whole wanna-be-rounded cables thing before rounded cables existed, i don't mess up with that again 😉