[rescue] imaging old Mac double density floppy disks

[Geoffrey S. Mendelson]

On Mon, Jun 19, 2006 at 03:24:24PM -0400, kevin wrote:
> Someone told me that the old Macintosh DD floppy drives (not the 
> SuperDrives of days past) were "special" and that it was not 
> possible to read older Mac formatted DD floppies using a PC 
> floppy drive.  Anyone know if there is any validity to this?  I 
> thought that none of that would be relevant if i was using dd 
> (i'm not mounting the disks, just trying to image them).

They are correct. The bit encoding is completely different, and the
drive uses a variable speed motor to keep the sector sizes the same.

It's not that the data is formated differently, the data is ENCODED
differently.

> Any ideas?

Buy a Mac with a 680x0 processor and ethernet. Use MacOS 7 or 7.5
(both downloadable) and Apple's Diskcopy (also downloadable) to make the
images. Then you can archive 400k (single sided) and 800k (double sided)
disks.

Geoff.

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