Major Jackyl wrote on 2025-11-23, 16:38:

Is there going to be a specific use-case for this, that ImageDisk can't/won't do? (seems unlikely, ImageDisk was well written, thanks, Dave!)

Guess it can work without a computer capable of executing a piece of software?

H3nrik V! wrote on 2025-11-24, 11:36:

Major Jackyl wrote on 2025-11-23, 16:38:

Is there going to be a specific use-case for this, that ImageDisk can't/won't do? (seems unlikely, ImageDisk was well written, thanks, Dave!)

Guess it can work without a computer capable of executing a piece of software?

Indeed. It also has a 50 pin header, and I have never seen a 50-pin floppy drive. Are we creeping into 8" floppies with that? Or maybe it's something else entirely.

The original shugart 8" floppy interface was indeed 50 pin. They paired it down to 34 with the minifloppy

That's a cool piece of kit! Would be neat to get it up and running! Always wanted to see one in action.

I've never used a "Floppy Exerciser", or seen one used, but we had a different model in our shop back in the 90's when I worked for Pepsi Co. It was left over from early 80's machines that used old 8" (and later 5.25) floppies. By the time I got there in the early/mid 90's, those were all upgraded or gone, so it never got used. Kinda wish I had attempted to save it from the recycle bin back then.

On a side note, there's a modern alternative, seen it earlier this year and forgot about it. Thought about building one, just because, even though I have zero need for one, but would still like to have . 🤣

This one doesn't image.

https://github.com/schlae/FloppyExerciser

I've seen the same model in the OP come up on ebay at least twice in the past couple years.

Very cool - I'd not seen one of these before!

The title says (Analog Imagedisk?) ...

If you are referring to my ImageDisk tool, does this device perform save/archive/restore of entire disks? (the main function of ImageDisk)

I don't see any mention/buttons that suggests this functionality...

Regarding "excercising" .. ImageDisk test/align function can do a lot, but it was never designed to do any sort of continuous "excercising" (in fact, as it was deigned to archive ancient media, you want to avoid any sort of continuous access!)

It's also limited by the capabilities of the Nec765 FDC design used in the PC. I *suspect* that this machine is not "analog" but contains a digital FDC within (the floppy interface is after all digital) but depending on it's capabilities it might be able to do more/less than ImageDisk.

I'd be curious to know it if can "read" non-standard format types (like Apple GCR)

maxtherabbit wrote on 2025-11-25, 00:01:

The original shugart 8" floppy interface was indeed 50 pin. They paired it down to 34 with the minifloppy

The PC FDC can in fact (for the most part) access 8" disk drives - I have information in the ImageDisk documentation on how to construct an adapter to allow connecting 8" drives to a PC.

I say (for the most part) because 8" drives use a signal called "TG43" which modifies it write slightly on Tracks Greater than 43
The PC FDC does support this signal, but it's multiplexed with another signal in a way not easy to drive without adding hardware.

(I offer 3 ways to work around this)

1- Do nothing, many 8" drives don't use TG43 and some that do will still write usable disks without it.

2- ImageDisk can output TG43 on a parallel port pin - you have to make a special cable, but fairly easy to do.

3- ImageDisk can also pause/prompt so you can "flip" TG43 with a simple switch.

This is almost never a problem, because 8" disks were never officially supported on the PC (I think I'm one of very few people who actually provided for such a configuration)
For the purposes of archiving and restoring vintage disks - the work arounds work and make it possible!

I'm 90% sure the one we had at work was the 103D. It looks right. Even found the manual for it.

DaveDDS wrote on 2025-11-25, 04:34:

The PC FDC can in fact (for the most part) access 8" disk drives - I have information in the ImageDisk documentation on how to c […]
Show full quote

maxtherabbit wrote on 2025-11-25, 00:01:

The original shugart 8" floppy interface was indeed 50 pin. They paired it down to 34 with the minifloppy

The PC FDC can in fact (for the most part) access 8" disk drives - I have information in the ImageDisk documentation on how to construct an adapter to allow connecting 8" drives to a PC.

I say (for the most part) because 8" drives use a signal called "TG43" which modifies it write slightly on Tracks Greater than 43
The PC FDC does support this signal, but it's multiplexed with another signal in a way not easy to drive without adding hardware.

(I offer 3 ways to work around this)

1- Do nothing, many 8" drives don't use TG43 and some that do will still write usable disks without it.

2- ImageDisk can output TG43 on a parallel port pin - you have to make a special cable, but fairly easy to do.

3- ImageDisk can also pause/prompt so you can "flip" TG43 with a simple switch.

This is almost never a problem, because 8" disks were never officially supported on the PC (I think I'm one of very few people who actually provided for such a configuration)
For the purposes of archiving and restoring vintage disks - the work arounds work and make it possible!

Yes I'm well aware, I routinely use IMD to backup/restore images of 8" disks with my pair of Tandon TM-848E drives. They internally generate the write current control signal.

You mentioned the 765 multiplexes a low write current signal on the direction pin, which is accurate, but it's important to note that most later FDC chips which were popular in AT clones and beyond don't do this .(e.g. Intel 82077, NatSemi PC8477B)

Since most implementations of the 765 in the PC world were fixed frequency, you run into a unfortunate reality that the vast overwhelming majority of FDC cards which people would find suitable for interfacing with an 8" drive (supporting 500kbps and FM operation) do not even have the multiplexed signal available.

StriderTR wrote on 2025-11-25, 01:08:

That's a cool piece of kit! Would be neat to get it up and running! Always wanted to see one in action. […]
Show full quote

That's a cool piece of kit! Would be neat to get it up and running! Always wanted to see one in action.

I've never used a "Floppy Exerciser", or seen one used, but we had a different model in our shop back in the 90's when I worked for Pepsi Co. It was left over from early 80's machines that used old 8" (and later 5.25) floppies. By the time I got there in the early/mid 90's, those were all upgraded or gone, so it never got used. Kinda wish I had attempted to save it from the recycle bin back then.

On a side note, there's a modern alternative, seen it earlier this year and forgot about it. Thought about building one, just because, even though I have zero need for one, but would still like to have . 🤣

This one doesn't image.

https://github.com/schlae/FloppyExerciser

this thing looks bad ass, I'm gonna have to build one

maxtherabbit wrote on 2025-11-25, 15:44:

... it's important to note that most later FDC chips which were popular in AT clones and beyond don't do this ...

Agreed, fundamentally the PC FDC has to only do "what a PC wants" and support for 8" drives wasn't wanted, so many (most) later chips for PCs which emulate the Nec765 don't implement anything not needed by the PC (cost/design-effort reduction I'm sure)

But... I can't talk about the many PC chipsets which incorporate FDC emulation, because I don't know or have any experience with many of them.

So... what I do is talk about the original PC FDC which is the Nec765 .. this is what IBM used in the 5150, and almost all later chipsets emulate it (often only the necessary partial emulation) - to do otherwise would cause problems with OSs which hav their own FDC drivers... If you used say a WD2797 (which has a bit more nomn-PC functionality), you could make a BIOS which covered it, and probably DOS (which uses BIOS) would still work, it's a completely differnet command set, and no drivers written for the 765 would work at all, meaning every OS with floppy drivers wojuld have to have "special" drivers for your PC.

TG43 is a minor problem - easy for IMD to provide workable solutiions ... bigger problem is for example - some "765 compatible" FDCs don't support single density at all - used in a lot of older systems, but never in the PC.

These incompatibilities are the main reason I developed and provide the TESTFDC tool, so that you can determine exactly how capable the FDC is in your particular system.
(and anyone seriously wanting to use IMD to archive/restore vintage media will likely want to run TESTFDC on a bunch of different systens to find a "good" one)