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Getting an 8" FDD working with an IBM 5170?

S

SunSpotter

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The goal here is to keep my AT as "true blue" as possible, so no BIOS swaps, or removal of the original controller card if at all possible. And ultimately to get the 8" drive working alongside the original MFM HDD, a 3.5" FDD and a 5.25" FDD.

However, the original AT controller card only supports up to 3 total drives: either 2 FDDs and 1 HDD, or the opposite configuration. It's also worth noting that the particular 8" FDD that I have is a Vista Computer Co. V-1100 DSDD dual external drive. In effect meaning it's two drives in one enclosure, so with a stock AT I couldn't even use 1 conventional FDD alongside my 8" drive as far as I'm aware. The biggest problem though, is that while I already have all the necessary cabling, and an FDADAP 50-pin to 32-pin adaptor, I'm not sure what controller card I should be looking for.

I'm also going to throw it out there, that this drive is not to be mistaken for the V-1000 or V-1200, in case anyone looks it up. I'm not completely sure why but my particular drive just doesn't exist on the internet, in spite of the fact that information on its predecessor and successor models can be found.

Anyways, unless there's some trick I'm unaware of it seems like the original AT controller card is out of the question. And I have reason to believe the original card for the 8" drive itself wouldn't be AT compatible even if I could find it. I did try using a 16-bit IDE controller once, but it seemed to interfere with the functionality of the MFM HDD, even after I played around with the jumpers to avoid an I/O address conflict, so maybe it's a problem with IRQ? Either way, I'm stuck in a position where I'm not really sure what the best way to proceed is, or what controller card I should be looking for.
 
SunSpotter said:
However, the original AT controller card only supports up to 3 total drives: either 2 FDDs and 1 HDD, or the opposite configuration.
Click to expand...
As far as I am aware, the subject card will simultaneously support up to two floppy drives and up to two hard drives.
The limitation you write of sounds like the limitation of the 5170's case/chassis.

The card's limitation of two floppy drives is because the card has only one connector for floppy drives, together with using the IBM twisted floppy cable.

SunSpotter said:
And ultimately to get the 8" drive working alongside the original MFM HDD, a 3.5" FDD and a 5.25" FDD.
Click to expand...
Confirm for readers that your desire is to use the 8" drive as a logical drive (e.g. E:) in DOS.
 
modem7 said:
As far as I am aware, the subject card will simultaneously support up to two floppy drives and up to two hard drives.
The limitation you write of sounds like the limitation of the 5170's case/chassis.
Click to expand...

The chassis should support two of each. One full height HDD on the left side, two half height floppy drives and one half height HDD on the right side.

47C45125-D1E0-4341-9B16-C6FA509493AE.jpeg
 
If you want to use the original FDC board, you need to add a second board capable of operating on a secondary I/O port.
If you want to replace your FDC board, then there are 4 floppy controllers (i.e. ones with a DC37 connector on the rear). Regular commercial ones as well as projects hatched here.

Then, it's mostly a matter of getting the right cable/adapter; the rest is software.
 
jafir said:
The chassis should support two of each. One full height HDD on the left side, two half height floppy drives and one half height HDD on the right side.
Click to expand...
In the past, I have tried to fit various half-height hard drives under the two floppy drives, but from memory, there are issues like the screw holes not lining up.
 
Keep in mind that for many/most 8" disk formats FM support is required. There are only a handful of addon FDC cards that support FM operation. Look for one using a DP8473 or a PC8477 controller IC. Rarer still is one that supports being jumped for secondary I/O port operation. Two that meet both these criteria I know offhand are the Adaptec AHA-1542B SCSI card and the longshine LCS-6815 floppy card
 
MicroSolutions Compaticard IV
Sysgen Omnibridge
DTK Mini-Micro 4
I think there's a card by Sergey/Andrew.
All use NSC FDCs.
WD1002A-FOX (uses WD37C65)

All have a BIOS and support 4 drives (including 1.44M)

Several DTC SCSI and ESDI cards have BIOS support for 3 and 4 floppy drives.
Some Future Domain SCSI controllers can easily be modified for 3 floppy operation
Many Ultrastor SCSI controllers have support for at least 3 drives.
 
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modem7 said:
Confirm for readers that your desire is to use the 8" drive as a logical drive (e.g. E:) in DOS.
Click to expand...

Yeah that's correct. So when everything is said and done it would be something like A:1.2mb drive, B:1.44mb drive, C:boot drive, E:8" drive 1, F:8" drive 2

modem7 said:
The card's limitation of two floppy drives is because the card has only one connector for floppy drives, together with using the IBM twisted floppy cable.
Click to expand...

Hmm, this makes me wonder. I have a 5.25/3.5 combo drive with an internal twist that only requires one cable connector to the FDC itself. My 8" drive works similarly. One internal cable connecting both drives but only one that leaves the enclosure. So now I'm wondering if I couldn't just have the first connector on the ribbon be the combo drive, then have the FDADAP adaptor connected to what would ordinarily be the B connector after the twist, with the adaptor obviously hooked up to the 8" drive itself. Is it possible that the controller card would be capable of operating all the drives in such a configuration? My previous understanding came from your site, but I assumed the limitation was something more abstract than the simple lack of additional floppy headers.

maxtherabbit said:
Keep in mind that for many/most 8" disk formats FM support is required
Click to expand...

Hmm, well I guess that means some of the 8" disks I have I'll be able to use and some not so much. I have a box of IBM Diskette 2D which I know are MFM encoded, so I guess the easiest way forward would be to just use those. Good advice with the ICs though, I'll look for those in the future. Side note: the only catch with the IBM disks I have is that they're 256 bytes per sector, not 512 like most IBM compatible formats, so I'm uncertain what kind of issues that will cause me in the future.

Chuck(G) said:
MicroSolutions Compaticard IV
Sysgen Omnibridge
DTK Mini-Micro 4
I think there's a card by Sergey/Andrew.
All use NSC FDCs.
WD1002A-FOX (uses WD37C65)
Click to expand...

A Compaticard IV would be the dream lol, unfortunately they're unobtanium unless I win the lottery either literally or figuratively. Some of those other ones look like they might be obtainable though, so I'll keep a lookout if necessary.
 
There were, IIRC), a couple of "parasite" cards made to expand 2-floppy cards to 4-floppy. Pretty simple really; decode the same DOR (port 03f2h) register, but supply added motor enable and drive select info. The card interposed itself in the floppy cable and provided the extra drive connection via a DC37F connector on the bracket.

Simple to implement with SSI.
 
Depending on what you are using it for, you might consider connecting those drives to a Kryoflux instead. Of course, a real PC is more fun :)

Pretty much the only way to get the drives as drive letters in addition to existing A: and B: is to add a secondary card with a configurable I/O address. As mentioned, it should support FM encoding.

With a combo 3.5/5.25 drive, both drive selects are already in use, so just adding anything else to the cable would conflict.

You COULD wire in a physical switch to switch the drive select line for the 5.25 1.2mb drive between the 5.25" and one of the 8" drives. From a BIOS/software perspective, an 8" drive and 5.25" 1.2mb drive look almost identical. (Of course, you would still want a card that supports FM)

256 byte sectors are not a problem for tools like ImageDisk or Teledisk. Keep in mind there are a few uncommon formats/encodings that IBM PC controllers can't read, and PC controllers don't support hard sectored media.
 
SomeGuy said:
Depending on what you are using it for, you might consider connecting those drives to a Kryoflux instead.
Click to expand...

Definitely the way to go if I were seriously concerned about archiving old data I had on 8" media, but that's not really the case right now. Right now, getting the drives working is more about nerd cred and my own amusement than anything else, except maybe the learning process itself since I didn't grow up with this kind of tech. Kryoflux just kind of feels like cheating to that end lol.

Chuck(G) said:
There were, IIRC), a couple of "parasite" cards made to expand 2-floppy cards to 4-floppy. Pretty simple really; decode the same DOR (port 03f2h) register, but supply added motor enable and drive select info. The card interposed itself in the floppy cable and provided the extra drive connection via a DC37F connector on the bracket.

Simple to implement with SSI.
Click to expand...

Something like that would be perfect honestly. Takes up no expansion slots, and keeps with the spirit of the project. I'm not completely sure I understand how the DC37F connector fits in, since I'm not familiar with that standard though. Either way, sounds like it would be hard to find an original, but you seem to suggest it would be a simple design. If anyone else in the community would be interested in a "parasite card" that breaks out support for 4 FDDs, feel free to comment, because I'd love to see someone pick up a project to create something like that. I'd do it myself but I just don't have the skillset unfortunately.

On a related note, while doing some research, I came across this old thread for a community made XT-FDC and was wondering what became of the project. I scrolled through and it seems like most of the links are dead, so it's hard to know what state of completedness it ended up in without reading through 51 pages.
 
SomeGuy said:
Pretty much the only way to get the drives as drive letters in addition to existing A: and B: is to add a secondary card with a configurable I/O address. As mentioned, it should support FM encoding.
Click to expand...
Either adding a secondary card or replacing the primary FDC with a 4 drive controller would work.
 
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