Acorn ADFS disks are pretty standard MFM encoded IBM scheme disks, although with different sector sizes and with the 0-based sector identifiers rather than 1-based sector identifiers. The index hole is ignored and sectors are written whereever, requiring FluxEngine to do two revolutions to read a disk.

There are various different kinds, which should all work out of the box. Tested ones are:

  • ADFS L: 80 track, 16 sector, 2 sides, 256 bytes per sector == 640kB.
  • ADFE D/E: 80 track, 5 sector, 2 sides, 1024 bytes per sector == 800kB.
  • ADFS F: 80 track, 10 sector, 2 sides, 1024 bytes per sector == 1600kB.

I expect the others to work, but haven’t tried them; get in touch if you have any news. For ADFS S (single sided 40 track) you’ll want -s :s=0:t=0-79x2. For ADFS M (single sided 80 track) you’ll want -s :s=0.

Be aware that Acorn logical block numbering goes all the way up side 0 and then all the way up side 1. However, FluxEngine uses traditional disk images with alternating sides, with the blocks from track 0 side 0 then track 0 side 1 then track 1 side 0 etc. Most Acorn emulators will use both formats, but they might require nudging as the side order can’t be reliably autodetected.

Reading discs

Just do:


You should end up with an adfs.img of the appropriate size for your disk format.

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