Thomas Harte wrote:
Although I'm aware that my USB drive may be hard coded somehow not to support anything other than the PC layout
That's pretty much it I'm afraid! USB floppy drives are seen as simple block devices, and the linear->CHS mapping is done inside the unit. I believe DD disks will always be treated as 9-sector 720K (and HD as 18-sector 1.44M), so be missing the 10th sector of each SAM track.
I have heard rumours of USB drives with an unofficial way to change the geometry mapping in the drive, but I've yet to find one myself. Until someone creates something like a USB CatWeasel, you'll be unable to access 10-sector disks on a Mac.
Even if I can't image original disks, is there any way I could use this drive for some sort of data transfer?
You'd be much better off with an Atom Lite board in the drive 2 slot, so you can share a Compact Flash card between SAM and SimCoupe. It's faster, easier and more reliable than dealing with floppies. Edwin can provide them if you're interested.
The USB drive situation could be improved, with specially crafted disks that lock out the 10th sector on each track. SimCoupe could assist by returning matching dummy contents for the inaccessible directory and data sectors. You still wouldn't be able to use existing 10-sector SAM disks, but 90% of the space would be usable on new ones.
Si
