Distribution Media Format


Distribution Media Format is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 kB of data on a 3½-inch disk, instead of the standard 1440 kB. As a side effect, utilities had to specially support the format in order to read and write the disks, which made copying of products distributed on this medium more difficult. An Apple Macintosh computer running Disk Copy 6.3.3 on the Mac OS 7.6 or later operating system can copy and make DMF disks. The first Microsoft software product that uses DMF for distribution were the "c" revisions of Office 4.x. It also was the first software product to use CAB files, then called "Diamond".
Comparison of DMF and standard 1440 kB 3½-inch diskettes:
1440 kBDMF
Tracks8080
Sectors per track1821
Cluster size512 bytes1024 or 2048 bytes
Root directory entries22416

DMF in the form of a 1680 kB Virtual Floppy Disk image and IBM Extended Density Format images are supported by Windows Virtual PC.