Joakim wrote on 2021-05-17, 17:32:
Oh and I thought mfm was something else than the inbuilt controllers. Maybe I am mixing it up with mfm hard disk drives?
So my understanding is that early floppy drives were FM coded, so one transition in a given window for a '0' and two for a '1'. The regular transitions made it easy to keep the receiving end in sync in case you had a long sequence of '0's. Then they changed to Modified FM, with a single transition in the middle for a '1', and no transition for a '0', unless the previous bit was a '0', in which case there would be a transition at the start of the window. More complicated, but each bit now only needed the space needed for one magnetic transition rather than two, so the bits/inch could be doubled. And there floppies stayed through to 2.88MB. The floppy controller has to figure out the data rate by trial and error by looking at the RDATA stream coming from the floppy, trying to sync a PLL to it, then trying to read some header information from track 0, complete with some deliberately malformed bits that the controller can use as markers.
Anyway, point being that the standard PC floppy controller has to handle MFM.
So, SD was FM coding, DD is MFM coding, and I think QD is going from 48tpi to 96tpi, HD is then going from 9 sectors to 18 sectors/side.
My guess is that with any floppy controller then the drive will be able to write/read 9 sector/80 track disks (so a sort of 720k 5.25"). Although the drive heads might not be able to move far enough for the last 10 tracks. I don't know whether you'll need a specific controller to handle 8 sector disks. If it does work then the formatted capacity will likely be around 560kB (512 bytes/sector * 8 sectors/track * 70 tracks/side * 2 sides).
Should I be ok with one of those regular slot floppy cables and somehow move the wires to different pins? (I don't have a cable.)
You can probably bodge something together to test by taking a regular floppy cable, then use a knife to cut along the cable to extract the individual strands you need, then cut, strip, lengthen and rejoin as needed (e.g. extract wire 6 and 34, cut them, strip the ends of 6 from the drive and 34 from the PC, then link them together with a joining wire). You might get away with just twisting the wires together as a test since none of these are particularly sensitive Data signals.
What a out storage media? I read somewhere that you should have quadra density dual disks for these drives, but I never heard of them.
Don't really know, other than that link, which seemed inconclusive.
Essentially, I started out thinking it'd be a simple case of rewire the cable, then realised there were some format oddities. I think it'll probably still work, but with possible odd behaviour. OTOH, and this is the main reason I keep floppy drives in my computer, the sound when booting should be great.