LoadDskF/SaveDskF

Revision as of 21:08, 12 March 2021

LoadDskF and SaveDskF are floppy disk imaging utilities by IBM. They have an associated file format, sometimes called DSK or SKF. The format was notably used for OS/2 service packs.

It most likely contains an image of a FAT12 filesystem.

Some files are compressed. The compression scheme is some form of LZW.

Format details

The LoadDskF documentation says "all diskette sectors are written up to and including the highest occupied data sector". So, uncompressed files can probably be converted to raw FAT/IMA format by deleting the header, and appending padding if needed.

Identification

Old format files start with bytes 0xaa 0x58.

New format uncompressed files start with 0xaa 0x59.

New format compressed files start with 0xaa 0x5a.

Software

• DIUNPACK Rel. 3.03 (1996-01-30) (OS/2 software)
• loaddf.zip - LoadDskF 1.16r (1993-01-14) and SaveDskF 1.14r (1992-05-26) - DOS and OS/2-compatible binaries; probably requires a floppy disk + drive.
• DSKXTRCT - Exracts files (uncompressed disk images only) (OS/2 software)
• dskdcmps - Decompresses compressed disk images (source code)
• MAKEDSKF - Utility for creating disk images (OS/2 software)

Sample files

• http://cd.textfiles.com/hobbesos2/2_1/SERVPAK/ - Old format
• https://archive.org/details/IBMOS22.11XR06200EnglishDiskettes -> "IBM OS2 2.11 - XR06200 - English - Diskettes.zip" → *.DSK - Examples of new format, uncompressed
• https://archive.org/details/OS2_Install_Disks → OS2_W3B-D1CD_2000-03-19.zip → DISK1.DSK - Example of compressed format