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Secondary FDC

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Xacalite

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Feb 13, 2015
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Warsaw
Hello.
So I've got a bunch of old PCs, mostly XT and 286 clones, and in order to exchange data with them I'm trying to build a "bridge" machine with three FDDs: 1.44MB, 1.2MB, 360KB.

I tried to accomplish this using a 386 with two FDC cards, but no luck - even though I jumper one of them to secondary address there's still some conflict which results in BIOS complaining about FDC problem, or errors reading diskettes in the drive connected to the primary FDC.
SDRIVE.SYS fails to load with my controllers.
ANADISK seems to work, but this solution is inconvenient and ugly.
Yes, I've read http://www.seasip.info/VintagePC/floppies.html , but didn't really help.

The controllers are tried are based on:
1. UMC UM8388
2. UMC UM82C862F
3. Winbond W83765P

Also, I tried Longshine LCS-6610F, an FDC-only card with its own BIOS, but no luck here either, its BIOS seems to only support primary address even though the card can be jumpered to secondary.

So, has anybody had any ideas making two FDCs cooperate in one PC? If so, please share the details.
 
Depends on the FDCs. I run 3 Compaticards in one PC, supporting 6 drives. Several drivers from 90s support dual controllers for other disk formats (e.g. EAGLE16.SYS).

There's probably one out there for IBM DOS floppies; in any case, it shouldn't be difficult to construct one.
 
Xacalite said:
Hello.
So I've got a bunch of old PCs, mostly XT and 286 clones, and in order to exchange data with them I'm trying to build a "bridge" machine with three FDDs: 1.44MB, 1.2MB, 360KB.
Click to expand...
I accomplished exactly this setup in my XT with just one card. It is the XT-FDC card :)
 
If your machines have serial or parallel ports you can use Laplink and save yourself a lot of time as well. With just parallel ports you could also use UNET - II which is a full parallel port server/workstation network. Then there's always DOS' Interlnk/Intersvr.
 
I'm surprised that no one's suggested one of the old-time dodges--use a DPDT switch to change drive selects and add a DRIVER.SYS line to your autoexec.bat. For example, in your case, you'd switch the drive and motor selects between the 1.44M drive and the 360K one and add a DRIVER.SYS for the 360K.

You could also pick up a Microsolution's Backpack floppy and run it from the parallel port. There are older SCSI controllers that will support (or can be made to support) 3 floppy drives on a single cable and at least one that supports 4 drives on a cable (DTC). There are various other floppy controllers that support 4 drives through two connectors (e.g. Sysgen Omnibridge, WD1002FOX-004, DTC MiniMicro 4, etc.).

In addition, there were a few ISA adapters that weren't floppy controllers at all, but performed the device switch by decoding I/O address 03F2 and "daisy chaining" the primary drive cable, doing the select switch automatically that I described above.

There really are endless ways to skin this cat. You could, for example, install NICs in machines and network them.

Or you can, as described above, use the Interlink/Intersvr trick.
 
I insist on using floppies, sometimes there's simply no other solution, after all in order to use COM/LPT/Ethernet/etc. networking one has to run some software, and it must be brought in on... floppies, exactly.

Compaticard, Microsolution Backpack, SCSI... OK, but such stuff is rather hard to obtain nowadays, isn't it?
XT-FDC... looks interesting, are they available for sale?

If everything else fails I'm probably going to get some early Pentium box and use USB for the third FDD. But I would like to use DOS, and I expect problems using USB in DOS.
 
I run 2 HD floppy drives off (a bootable 1.44 and a 1.2M) off of a FDC with its own BIOS plus chain an additional external backpack 1.44MB floppy, a backpack CD-ROM, and a Zip 100 off of the parallel port. I also have a spare high density FDD controller for sale, tested,with a 1.44MB internal drive, 5.25" bay adapter, and cable on eBay of you or anyone else is interested.

Mike
 
I've done this, and have one controller left that likes it, but it is an 8-bit card and a little slow, but does what i want it to.

Disable the onboard controller if it has one, or tell the bios there are NO floppies, use the card that has its own bios, high densities on one connector, low densities on the other
 
I ran 3 floppies, a 1.44, a 1.2 and a 360 for over 10 years on a 286. The 360 was outside the case. I ran a molex power cable and the A drive ribbon connector outside the case as well. With this double card edge adapter...

P4200140.jpg

... I could choose which 5.25" I wanted to use and would manually switch between the two 5.25" drives, one inside the case and one outside the case. Of course, I needed to reboot the machine and reconfigure the CMOS each time I changed the physical cabling.
 
This probably won't work with a 386, but if you have a Pentium-class computer you can use an IDE LS120 drive for 1.44MB support and put the 360K and 1.2MB drives on the floppy controller.
 
Plasma said:
This probably won't work with a 386, but if you have a Pentium-class computer you can use an IDE LS120 drive for 1.44MB support and put the 360K and 1.2MB drives on the floppy controller.
Click to expand...
My 286 with a parrallel port LS120 works, so there's no reason it can't work on a 386. No need to disconnect any drives from connectors at all either. So 1.2meg & 360k drive internally with an external parallel port LS120 drive for 3.5" 1.44 meg and 720k support.

Also you should be able to use an IDE LS120 drive on any IDE controller if you have suitable dos drivers for it on a 386 class system. Not unlike using an IDE CDrom in dos.
 
Last edited:
Was thinking in terms of BIOS support. Later BIOSes have native support for LS120 so you can boot from them.
 
(I hope this gets through the moderation...)

Oh yeah, I forgot about LS-120 - as far as I remember this has good DOS support, and with great many BIOS'es it's even bootable.
And I think it's easier to obtain than all the other alternatives, so that's probably the path I'm going to choose...
 
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