IBM Extended Density Format

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The eXtended Density Format (XDF) is a way of formatting standard high-density 3.5" and 5.25" floppy diskettes to larger-than-standard capacities. It is supported natively by IBM's PC-DOS versions 7 and 2000 and by OS/2 Warp 3 onward, using the XDF and XDFCOPY commands (directly in OS/2).

When formatted as XDF disks, 3.5" floppies can hold approximately 1.86 MiB, and 5.25" floppies can hold 1.54 MiB, using different number of sectors as well as different sector size per sector (not all sectors in the same track are of the same size). However, the first cylinder uses standard formatting, providing a small FAT12 section that can be accessed without XDF support and on which can be put a ReadMe or the XDF drivers.

Floppy distributions of OS/2 3.0, PC-DOS 7 and onward used XDF formatting for most of the media set.

[edit] Competing format

Description of XDF specifics