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jfdelnero / HxCFloppyEmulator

HxC Floppy Drive Emulator toolkit
https://hxc2001.com/floppy_drive_emulator/
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Acorn ADFS/DFS 800K and 1.6MB format support #22

Open philpem opened 2 months ago

philpem commented 2 months ago

I noticed there were some XML files which describe the Acorn ADFS S/M/L (small, medium, large) disk formats in the Git repo. Sadly there aren't any for the newer (RISC OS) formats. I'm providing some information on them in case you want to add the other formats.

It also appears that the ACORN_ADF loader is read-only (unlike the AMIGA_ADF loader) - it would be useful to have read-write support for these. In the interim I'm probably going to use Imagedisk as an intermediate format so I can detect missing or corrupted sectors.

If you'd like reference information on these formats, Gerald Holdsworth has documented them: https://stardot.org.uk/forums/viewtopic.php?t=14423

These are all 3.5-inch formats.

D, E and E+ are 80 tracks double-density MFM, five sectors per track, 1024 bytes per sector, giving 800K without filesystem overhead.

F and F+ are 80 tracks high-density MFM, ten sectors per track, 1024 bytes per sector, giving 1600K without FS overheads.

There's also a "G" format which seems to be ADFS on a "2.88MB" disk, giving 3200K by increasing the density and doubling the sectors per track. I've never seen this in the wild.

In terms of the naming convention, D is 800K with an old-type (BBC style) disc map. E and F use a new-style map. E+ and F+ extend the new-style map with long filenames (RISC OS 4). This is all filesystem level stuff, so if you're only concerned with the ADF files, you can just call them "D, E or E+" and "F or F+".

In case it's relevant - ADFS S and M (Small and Medium) are usually seen on 5.25-inch BBC disks. ADFS L (Large) 640K can exist on either double-density 3.5-inch or 5.25-inch disks and is/was sometimes used for data interchange between later BBC Micro (Master 128 or upgraded BBC B) and Acorn Archimedes (RISC OS) systems.

jfdelnero commented 6 days ago

Is there any stream dump available for these formats ?

philpem commented 5 days ago

Is there any stream dump available for these formats ?

I can format one in the machine on a Flashfloppy if that would help. What format would you prefer?

Otherwise if I can find some blank disks I can send you an image done with a Greaseweazle.

jfdelnero commented 5 days ago

i have no preference, so more formatted hfe i get, better it is ;)