2.5 KiB
Disk: Apple II
Apple II disks are nominally fairly sensible 40-track, single-sided, 256 bytes-per-sector jobs. However, they come in two varieties: DOS 3.3/ProDOS and above, and pre-DOS 3.3. They use different GCR encoding systems, dubbed 6-and-2 and 5-and-3, and are mutually incompatible (although in some rare cases you can mix 6-and-2 and 5-and-3 sectors on the same disk).
The difference is in the drive controller; the 6-and-2 controller is capable of a more efficient encoding, and can fit 16 sectors on a track, storing 140kB on a disk. The 5-and-3 controller can only fit 13, with a mere 114kB.
Both formats use GCR (in different varieties) in a nice, simple grid of sectors, unlike the Macintosh. Like the Macintosh, there's a crazy encoding scheme applied to the data before it goes down on disk to speed up checksumming.
In addition, a lot of the behaviour of the drive was handled in software. This means that Apple II disks can do all kinds of weird things, including having spiral tracks! Copy protection for the Apple II was even madder than on other systems.
FluxEngine can only read well-behaved 6-and-2 disks. It doesn't even try to handle the weird stuff.
Apple DOS also applies logical sector remapping on top of the physical sector numbering on the disk, and this varies depending on what the disk is for. FluxEngine can remap the sectors from physical to logical using modifiers. If you don't specify a remapping modifier, you get the sectors in the order they appear on the disk.
Reading discs
Just do:
fluxengine read apple2
You should end up with an apple2.img which is 143360 bytes long. It will be in
physical sector ordering. You can specify a sector ordering, --appledos or
--prodos to get an image intended for use in an emulator, due to the logical
sector mapping issue described above:
fluxengine read apple2 --prodos
You will also need this for filesystem access.
Writing discs
Just do:
fluxengine write apple2 -i apple2.img
If your image is in logical sector ordering (images intended for emulators
usually are), specify a modifier of --appledos or --prodos:
fluxengine write apple2 --prodos -i apple2.img