Can a 1581 drive be made to read Amiga floppies?

[Ral-Clan]

Since the Commodore 1581 3.5" floppy drive is a re-programmable smart drive which uses the same drive mechanism as early Amigas (A1000, A1010 and maybe A500) - and since the 1581 can be made to read Double density PC disks, etc, can the 1581 be reprogrammed in software to read Amiga floppies?

I know there is software that will allow Amigas and even Windows PC's to read and write to a 1581 CBM-DOS floppy using the computer's internal 3.5" drive.

I already have a cable which allows me to hook real Commodore disk drives to my PC, so I'm wondering if it would be possible to write Amiga disks from disk images (.adf) to a real Amiga floppy (usable in a real Amiga) with the 1581 drive hooked to the PC (provided some software to do so exists).

From what I understand, the problem with PC floppies drives is that they are "dumb" and not re-programmable, so cannot be made to write/read AmigaDOS floppies....but in theory shouldn't hooking a re-programmable "smart" 1581 floppy to a PC overcome that hardware limitation and make it possible to write any sort of double-density format disk (Atari, Apple 800K, Amiga) provided software existed handle the new DOS format?

I'm aware of Catweasel and other projects that already exist...

EDIT: I've been reading that 1581 floppes are MFM formatted, and Amiga formatted disks are not - so maybe that's the limitation.

[mongo]

Since the Commodore 1581 3.5" floppy drive is a re-programmable smart drive which uses the same drive mechanism as early Amigas (A1000, A1010 and maybe A500) - and since the 1581 can be made to read Double density PC disks, etc, can the 1581 be reprogrammed in software to read Amiga floppies?

I know there is software that will allow Amigas and even Windows PC's to read and write to a 1581 CBM-DOS floppy using the computer's internal 3.5" drive.

I already have a cable which allows me to hook real Commodore disk drives to my PC, so I'm wondering if it would be possible to write Amiga disks from disk images (.adf) to a real Amiga floppy (usable in a real Amiga) with the 1581 drive hooked to the PC (provided some software to do so exists).

From what I understand, the problem with PC floppies drives is that they are "dumb" and not re-programmable, so cannot be made to write/read AmigaDOS floppies....but in theory shouldn't hooking a re-programmable "smart" 1581 floppy to a PC overcome that hardware limitation and make it possible to write any sort of double-density format disk (Atari, Apple 800K, Amiga) provided software existed handle the new DOS format?

I'm aware of Catweasel and other projects that already exist...

EDIT: I've been reading that 1581 floppes are MFM formatted, and Amiga formatted disks are not - so maybe that's the limitation.

I'm not sure what you consider a "re-programmable smart drive". The 1581 uses a floppy disk controller IC not that much different than the one used in a PC. You might be able to read an Amiga disk with it using the Read Track command, but you will not be able to write one, even using the Write Track command.

Amiga disks are MFM formatted.

[psxphill]

I'm not sure what you consider a "re-programmable smart drive".

It's got a cpu that can execute code, which might mean you could perform some tricks to get the WD1770 to do things it wasn't designed to do.
 
However if it is possible, then I don't know of anyone that has done it.
 
You can mount 1581 discs on an Amiga though.

[commodorejohn]

Both Amiga and 1581 disks are MFM-encoded as opposed to the 1541's GCR encoding, so it might be within the realm of possibility, actually. It's certainly not going to be supported by the drive firmware, but luckily the CBM 8-bitter drives have enough onboard RAM to allow for significant reprogrammability. There's already utilities that finagle it into reading and writing PC floppies, so I don't see why it couldn't be tweaked to support Amiga disks.

[Zac67]

Reading could be difficult due to the Amiga writing a complete track at once with a single sync - the 1581 would require enough RAM to buffer the track. Possibly you could be able to use a clever scheme to read a track in more than one step. Additionally, the drive would be required to learn OFS.

Writing most probably is impossible since the track must be written in one piece.

[mongo]

There's already utilities that finagle it into reading and writing PC floppies, so I don't see why it couldn't be tweaked to support Amiga disks.

It can't support Amiga disks for the same reason a PC floppy controller can't support Amiga disks. The Amiga reads or writes a whole track at a time. There's no gaps between sectors like there are on a PC floppy (or a 1581 one). That's why you can fit 880k on an Amiga floppy and only 720k on a PC one. You cannot write a whole track of data to a disk with the controller in the 1581, even with the Write Track command, even if you had enough RAM.

[commodorejohn]

It can't support Amiga disks for the same reason a PC floppy controller can't support Amiga disks. The Amiga reads or writes a whole track at a time. There's no gaps between sectors like there are on a PC floppy (or a 1581 one). That's why you can fit 880k on an Amiga floppy and only 720k on a PC one. You cannot write a whole track of data to a disk with the controller in the 1581, even with the Write Track command, even if you had enough RAM.

Ah, gotcha. Interesting...

[LoadWB]

No "finagling" required to get the 1581 to read PC-formatted floppies.  It's an MFM drive and the code is built into DOS to read it DOS-formatted.  It's not native, but it can do it with the right commands.

How would the 1770 (or 1772 in some models?) react to a gapless track?  Would it be possible to just keep re-reading the track and capturing chunks of the data stream?

Get the track sync, read 512 bytes.  Get the track sync again, read the next 512 bytes.  And so on.  My guess is no, since it would seem the data would come from the disk much to quickly to "stream" and the controller would essentially buffer then DMA the sector to drive memory.