Creating an image of the floppies, once you can read them, is easy enough. The problem is finding the hardware which can read them.
At the time that 3½ inch floppies where common there were three wide spread systems which wrote to them:
- The IBM compatible PC, which kept their rotation speed constant. These used up to 720KB of the maximum of 1MB which could be stored. Using 80 tracks on 18 sectors like this. TRACK GAP. sector 1, sector gap, sector 2, sector gap, ....
- Amiga's, which skipped the inter-sector gap, and wrote 11 sectors per track. That allowed them to store 880KB.
- Macs, which varied the rotation speed.
If you do not vary the rotation speed then the outside part of a disk will pass much more quickly beneath the RW head. This does not optimally use the capacity of the disk. So the Mac was smart and varied speeds.
The downside to this is that you need a drive which can do that, and the mac was the only common computer of that era which did that.
All of this means it that you need some non-standard-pc hardware to read the disk. Once you have that it is a simple matter of using
`dd if=/dev/floppy of=/home/mybackup bs=84. Once you have them as an image you can open them with a recent Mac OS/X. (OS/X 10.4 has read only access, so I guess just for backing them up modern is not even needed).
That leaves the problem of getting the right hardware. Sadly the only answer to this seems to be to find an old Mac.
There seem to be two solution for the PC:
- Kryoflux which samples the disk to a raw data stream. Getting the actual files out might not be entirely trivial, but once you have the data it should be possible,
- Disk ferret
Both use their own hardware rather then a PC floppy controller.