Macintosh Floppy Drive to PC Controller?

[MarNo84]

Hey folks,

I'm thinking about a new project to start...and therefore I wanted to use a Apple Macintosh floppy FDHD a.k.a. superdrive on a regular PC mainboard/floppy controller.

I've got some of these drives around in a box.

Is this even possible?

I know it's kinda different controller/hardware etc. - it should be possible? I know that for example on IBMs PS/2 the drives are similar difficult to adapt because of different wirings: power+data in one cable - you have to split it at the pcb side.

Same or similar goes for the Mac drives?

I think it's just a wiring ) cabke issue?

I just want to use these functions like autoeject etc. - FYI - that project involves also a MacOS on PC HW thing

Marcus

 

[Gorgonops]

So, long story short, no, it's not just a cabling thing. Macintosh floppy drives use a completely different signaling protocol for sending low-level commands for functions like head positioning.

(TL;DR: Mac floppy's drives' version is more sophisticated/complicated. The Shugart/PC drive interface is essentially completely "dumb" in that it is not reliant upon any state being maintained by the drive and a separate wire is used for every function. Apple 3.5" floppy drives use four "PHASE" lines, which are re-purposed from the lines used to directly drive the stepper motors in the original 5.25" Disk ][ , to relay discrete instructions to a state register inside the drive itself. And the computer can also read state from this register; there's nothing analogous in PC drives.)

It might theoretically be possible to put a small microcontroller between the PC interface and the Mac drive to translate between the two, but it'd be non-trivial exercise. Also, obviously, you'd be on your own in getting things like autoeject to work. I don't see any way of doing so without writing a software driver and, probably, wiring up the eject function to some other I/O port. (I suppose if you did the microcontroller thing you might be able to trigger it by writing your own replacement floppy driver that can signal an eject by doing something "weird" with the control lines. It is *possible* to drive things other than normal floppy drives with PC floppy controllers; backup tape drives that used the floppy controller as the data pump were common once upon a time and likewise overrode the usual functions of the control lines for their own nefarious purposes.)

The lazy way out if all you want is an auto-ejecting floppy on a PC would be to lay your hands on an old LS120 SuperDisk Drive. They support the same eject command as CD-ROM drives and work fine for reading/writing normal 1.44MB floppies. Had one in my desktop PC back at the turn of the century and it was a fun novelty. Granted they're a bit thin on the ground now.

 

[MarNo84]

Ah ok - right - this makes sense :-/

Well then I think I'll stick with one of those LS120 drives

 

[trag]

I think the data encoding is different on Macintosh 400K and 800K disks as well.   IIRC, both Macs and PCs encode data on 1.44MB floppies using an MFM scheme.   But on the lower capacity disks, Macs use GCR encoding.  This means that any driver/hardware for a Mac floppy must be able to decode both MFM and GCR (unless the data separator is built into the Mac floppy drive).   I'm not sure about that, but I don't think it is.

 

[Gorgonops]

I think the data encoding is different on Macintosh 400K and 800K disks as well...

My assumption when concentrating on the "control line" aspect of the problem was that the OP would be satisfied with just using MFM formats; obviously the problem gets that much larger if the ask is to enable it to read/write the GCR formats because not only do you need controller support there's the issue that the Mac floppy drive runs at variable speed in that mode. (Actually... maybe that wouldn't itself be an issue because on all drives after the original 400k the drives regulate the speed themselves instead of depending on a PWM signal from the computer... but still.) I don't *think* there's any data separator hardware, etc. on the Mac drives themselves that would rule out cross-connecting the R/W signals for the head to a PC controller's R/W lines... but I don't definitely *know* that they're electrically compatible either. Guess is yes, but, still, you've got the control issues to deal with first.

 

[bibilit]

can be found.

https://www.leboncoin.fr/informatique/1338170670.htm?ca=12_s

not in your country though