For the Atari ST, if you are going to download abandonware, different sites will use different formats:

  • .ST : perfect for disks that don’t require a specific format, supported by #greaseweazle.
  • .MSA : better for custom formats, supported by #greaseweazle.
  • .STX : supposedly capable of storing some copy protections, but a pain to work with; can be read and converted by HxCFloppyEmulator.
  • .IPF : good for archives of copy protected software.
  • Raw formats: only use when no other alternative.

However, if you need to archive your own disks and those have copy protections in place, you may need to use one of “RAW tracks” formats below, for example .SCP.

Basic formats (Data Only)

.ST

  • Same as .IMG, .IMA, .DSK
  • No meta data at all
  • Does not retain sector interleave
  • Does not support copy protection schemes
  • Supported by #greaseweazle

These formats store the payload data of all sectors back-to-back, in logical order, with no separators and no metadata.

The sectors appear in increasing logical order of Track #, Head #, Sector #. Physical layout attributes such as sector interleave are not represented in these image files.

For example on a double-sided, 80-track, 9-sectors format, the order of sectors in the file will be:

  • T0 H0 S1, T0 H0 S2, …, T0 H0 S9
  • T0 H1 S1, T0 H1 S2, …, T0 H1 S9
  • …
  • T79 H1 S1, …, T79 H1 S9

Since these image types do not describe the physical disk and track layout, they can only be handled by Greaseweazle in concert with a specified --format.

Advanced formats (with MetaData)

.MSA

  • Includes a header with
    • # of sectors per track
    • # of sides
    • # of tracks (start and end tracks to be precise)
  • Data follows the header in the same order as in .ST but each track has a mini header indicating the data length
  • Each track may be compressed by an RLE (Run Length Encoding) algo. In that case the data length will be less than # of tracks * 512.
  • Supported by #greaseweazle

.DIM

  • Includes a header with:
    • # of sides
    • # of sectors per track
    • # of tracks (start and end tracks to be precise)
    • Double Density vs High Density
    • Copy of Bios Parameter Block of the disk
  • Data follows the header in the same order as in .ST
  • The header contains a flag to indicate whether unused sectors have been removed or not. If yes, the FAT must be read in order to know which sector is which.

.STX “Pasti”

  • Many issues. Try to use other formats if possible.
  • Used by the Steem emulator and a package of tools for disk imaging called “Pasti”
  • Format was not properly documented by its author
  • Data is organized by tracks, where each track has its own “descriptor” meta data; in it, each sector also has its own “descriptor” meta data.
  • Can be read and converted by HxCFloppyEmulator.

.IPF (Interchangeable Preservation Format)

  • Universal ‘Golden Image’ Format
  • Supported by #greaseweazle (for writing to disk only)

.STT

I have never encountered this one yet. Details here.

  • Includes meta data

RAW tracks formats

.HFE

  • Stores Raw Bitcells, 1 revolution per track
  • Supported by #greaseweazle
  • No automatic verification is performed

.SCP

  • Stores Raw Flux, multiple revolutions per track
  • Supported by #greaseweazle
  • No automatic verification is performed (different revolutions may contain different read data)

.RAW (Kryoflux)

  • 1 file per track and per side with names like name<track>.<side>.raw
  • Stores Raw Flux, multiple revolutions per track
  • Supported by #greaseweazle
  • No automatic verification is performed (different revolutions may contain different read data)