einr wrote:

Hey all, […]
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Hey all,

So the situation is this: I have a 486 system with a 3,5" A: drive and a 5,25" B: drive, and I want to keep both but also install a Gotek floppy emulator.

Of course the floppy controller only supports two floppies, so I was wondering if one can easily build something to physically switch between the real A: drive and the Gotek as A:? Essentially the equivalent of pulling out and replacing the data cable, but with a switch.

I don't really know enough about floppy signalling to figure out how to do this right. Maybe there is some kind of ready-made solution?

The answer is to switch the Motor Enable B and Drive Select B lines between the two drives. (Note the cable twist makes Drive A turn on with the "B" lines...)
This requires a double pole/double throw switch, (one pole for Motor Enable, the other pole for Drive select) common connected to the motherboard inputs, and the contacts connected to the drives.
All other signals from the motherboard feed both drives directly.

The floppy cable is multiplexed - only the selected drive will listen and send data.

When the switch is in one position, it sends Motor Enable and Drive select to the corresponding drive, and it becomes active.
The Motor Enable and Drive select for the other drive remain inactive, and it remains dormant. (the beauty of open collector driven outputs)

That's the simple bit, the hard bit is actually implementing it.
I would suggest a length of 34w ribbon cable, a 34W IDC plug, and two 34W idc sockets.
The sockets are mounted on the cable to allow direct connection to the gotek and the 3.5" drive, and with sufficient distance between all connectors to allow the wires carrying Motor Enable and drive select to be split out for each connector, which are then extended out to allow them to be soldered to the switch mounted in a convenient location.

Thanks for explaining so clearly. It should be easy enough to make, problem is how to fit it and make it look nice and tidy I guess. I'll update the thread when I get it done 😉

what about second ide (hdd+floppy) controller? wont work? I have simmilar issue - I have floppy 3.5 & 5.25, and I have QIC80 IOMEGA TAPE 250 and dont know how to have all 3 drives working.

retropol wrote:

what about second ide (hdd+floppy) controller? wont work? I have simmilar issue - I have floppy 3.5 & 5.25, and I have QIC80 IOMEGA TAPE 250 and dont know how to have all 3 drives working.

A second floppy or multi I/O controller would probably work, assuming you can set it to use resources that don't conflict with the first one.

MS-DOS supports four floppy drives, you might have to use DRIVPARM or DRIVER.SYS to set them up, but it absolutely should work.

There are a few problems for me with this setup, though:

1) this means one of the floppy drives will end up as D: and some software really doesn't like floppy drives that aren't A: or B:

2) the third floppy drive won't be bootable since BIOS won't see it

2) I'm not sure I have space for more ISA cards in my machine 😀

IOMEGA TAPE250 is not seen in bios or os. It has no letter assigned. I need to have dedicated sw to run to interop with iomega. This is how it works.
My issue is if there will be any limit on the ribbon cable. I have double-connector (two sections) ribbon - one section is used by me for 3.5 (on the far end - to have this as A: and bootable), second section is used by me for 5.25. Where and how to connect IOMEGA? Should I just use extension fdd ribbon cable and connect to any of the connectors left on both sections (near 3.5 - the 5.25 conector is free, near 5.25 - the 3.5 connector is free)? And I do not need the controller then?

retropol wrote:

IOMEGA TAPE is not seen in bios or os. It has no letter assigned. I need to have dedicated sw to run to interop with iomega.
My issue is if there will be any limit on the ribbon cable. I heve doble connector ribbon, one section is for 3.5 (on the far end - to have this as A: and bootable), second section is for 5.25. Where and how to connect iOMEGA Should I use extension fdd ribbon cable and connect to any of the connectors left on both sections (near 3.5 - the 5.25 conector is free, near 5.25 - the 3.5 connector is free)? And I do not need the controller?

A normal PC floppy cable can only support two drives even if there are four drive connectors. There are four connectors so you can connect either a 5,25" or a 3,5" drive as A: or B:. You cannot use both connectors before or after the twist in the cable.

What you need to do for your tape drive is install another floppy controller card and use an entirely separate cable.

EDIT: then again, maybe not...

retropol wrote:

what about second ide (hdd+floppy) controller? wont work? I have simmilar issue - I have floppy 3.5 & 5.25, and I have QIC80 IOMEGA TAPE 250 and dont know how to have all 3 drives working.

That's a different problem.
The tape drive probably requires some kind of driver.
The driver probably speaks directly to a floppy disc controller (FDC)at a specific address.
If you can either configure the driver to speak to a second FDC, or hack the code to do the same thing, then using a second FDC at an alternate address is an option.

Focus on the driver - back in the day, programmers were flexible - it wouldn't seem that mad to have a computer with two floppies (=primary FDC tied up), a hard drive, and an owner who wants to install a tape drive hanging off a floppy interface (remember SCSI=$$$/£££).

Having said that, just how frequently do you want to swap between two floppy drives and 1 floppy+1 tape drive???

DX4 - wow, where you get this article? 😀 nice! thanks! so it means my idea of usage fdd extension ribbon and connect anywhere to free connector of my existing fdd ribbon which is already hosting the 5.25 and 3.5 should work... GREAT!

retropol wrote:

DX4 - wow, where you get this article? 😀

PC Magazine, 29 sep 1992 😀