NABU floppy disk format

The DPB is stored on-disk in the post-index gap data on track zero. This means a disc which has been copied sector-by-sector (e.g. with ImageDisk) won't boot or be recognised on the NABU. I don't know if a HFE image (on a Gotek running FlashFloppy) will work as I haven't tried it.

The DPB data can be displayed using the raw data viewer in FluxEngine. Finding the sync point may require some finesse.

At the time of writing I'm not aware of a tool which can analyse a flux image (e.g. SCP) and extract the DPB data. This would need the flux timing data to be converted to MFM-encoded bits, the sync point found, and the gap data extracted.

Sadly the DPB data is missing the sector interleave information.

CP/M uses a Disk Parameter Header and Disk Parameter Block to specify how data is stored on disk.

The BIOS on the system may also choose to implement sector interleaving below the CP/M BIOS/BDOS level.

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  • Last modified: 2023/10/03 15:23
  • by philpem