Maybe this is of any help? Probably a master and slave problem.

A question about 3.5 floppy drive and a 5.25 floppy working together...

The last comment is about a thing i noticed myself a lot trough the years: with some cables it is not always clear how it goes on the drive (sometimes the connector needs to be plugged in upside down to get the pin 1 ''stripe'' in the right place. 5.25 connectors can be reversed too).

The 5.25 floppy connection is a card edge with a split, something like AGP: physically impossible to get backwards. I had also verified that all jumpers are in their default position which means drive assignment is strictly cable and BIOS. Strange part is my 3.5 floppy does not work on that cable either no matter what connection order I try (but the other, single-drive cable works perfectly). Is there any other way to be certain whether or not the fault lies in the cable itself?

If the 3.5 won't work on it's own on that cable, but will on another, then the cable must be at fault.

NB. For the 5 connector / 2 drive cable, traditionally both drives were jumpered as B, the one after the twist taking A.
With a single untwisted cable, the drive would be jumpered as A

There is also a terminator jumper, or sometimes a terminator pack, which should be removed on the middle drive out of 2

The single cable does have the twist, so everything adds up there.

Know a good source for a reliable cable? The one in question was picked up at a computer parts and service center in Garland, TX.

Getting the 1.44Mb 3.5" drive and the 5.25" floppy drive and the ZIP100
all working together is probably achieveable, but without more information
it's non-trivial to give you advice on how to proceed.*
In regard to "getting the floppy drives by themselves working together",
try this (with the Zip100 disconnected from the system to simplify testing);

You replied to Matth79 that "The single cable does have the twist", so I will
assume the 1.44Mb 3.5" floppy drive has its' jumper set as Drive Select B
(yep B), and that the AX6BC bios had/has the following settings;
'Floppy drive type' set Drive A to 1.44Mb 3.5" and set Drive B to (whatever
capacity your 5.25" floppy drive is), and 'Onboard FDC controller' set Enabled,
and 'Swap floppy Drive' set Disabled.
Check that the 5.25" floppy drive has its' jumper set as Drive Select B (yes B).
Connect the 5 connector/2 drive cable (which should have only one twist {not
two separate twists} in the cable) to the motherboard, with the 1.44Mb 3.5"
on the end position of the cable and the 5.25" on the middle position of the cable.
Tell us if it is working now.
{For reference; http://pinouts.ru/Storage/InternalDisk_pinout.shtml }
===========

*(Info like what make/model is the hard drive and how is it jumpered,
how is the Zip drive marked on its' sticker, e.g. atapi or atapi2, and how is it
jumpered, in the bios for the particular channel position the ZIP is connected
on the 'Hard Disk' 'Type' is set to what e.g. Auto/None, and what is set for
'Hard Disk' 'Mode', is your bios version R2.20 (1/26/1999) or later, what make/
model is the CDROM and how is it jumpered, what ZIP100 manual do you have
(if any) and do you have the Iomega ZIP (software) setup.exe-guest.exe-
Iomega Zip IDE/ATAPI driver-Iomega Zip format utility, have you made back
ups of data on your ZIP disks, what make/model is the 5.25" floppy drive...)

Been busy lately, but I can let you know for sure the 5.25 drive is a TEAC 7193U (I purchased this very specific make and model for compatibility purposes). I recall verifying all floppy jumpers were in their default position according to documentation I found through Google for the 5.25 (I know the 3.5 is read as A: when using the single cable so that must be configured correctly) which is what seemed to narrow it down to a cable issue. As for my BIOS options, you presume correctly about every single one though I tried tweaking some of those options [before restoring to defaults] just to rule it out as a BIOS issue. Also, it so happens I had used your provided link as a reference before posting this problem.

I may be able to re-check everything and run more tests tomorrow. In the meantime, how would I find my BIOS version and (short of completely pulling them out of the tower) the exact makes and models of my other drives?

I have read that "Floppy drive light(s) stay continuously on" can be a symptom of
floppy connector inserted into 3½ drive the 'wrong' way, but as you are obviously
fully conversant in these matters, we'll discount that.
(For benefit of viewers, perhaps we should state that the 5¼ drive jumpers are set
DS1 bridged, and DC bridged, all other jumpers unbridged, and throw in a pic as well; 😀
http://nfggames.com/x68000/Documentation/Flop … er_settings.jpg )

Regarding "how would I find my BIOS version" http://ankyo.rulez.jp/cpu/BX_1200_02.jpg
The reason bios version may have an impact (when later ZIP100 is attached) is this
note for Bios R2.20 (and applicable to later Bios versions) at http://global.aopen.com/products_download.aspx?auno=299
"Supports Panasonic ZIP drive to be configured as either Floppy_A: or Non_Floppy_A:"
(Regarding other drives, info may be helpful during later fault checking and if you
later decide to move the ZIP100 so it is not sharing a channel with the C: drive.)

Hi,

"IOMEGA ZIP 100 ATAPI Floppy"

...might be, that you by accident jumpered the ZIP as "Master A" or "Slave A" ?

I do this most times, having no more floppy drives to care for and having A: as bootable medium with 100MB...

greetings duncan