High density (floppy disk)
High Density , or HD for short , is one of several possible recording densities on floppy disks . It is used for 3.5 ″ and 5.25 ″ diskettes with a physical storage capacity of 1,500 KB (5.25 ″ diskettes) and 2,000 KB (3.5 ″ diskettes).
With normal formatting with 80 tracks and 18 sectors, 3.5 ″ HD disks have a capacity of 1,440 KB and a track density of 135 tpi , 5.25 ″ disks have a format with 80 tracks and 15 sectors Capacity of 1,200 KB, with a track density of 96 tpi. HD disks are usually backwards compatible, so they can also be formatted as DD disks if necessary . In order to write to and read from HD disks, HD-capable disk drives are required, but these have long been state of the art.
A 3.5 ″ HD floppy disk, in contrast to a 3.5 ″ DVD diskette, has two identification holes for identification.
It is relatively common for 3.5 ″ HD floppy disks to be overformatted to provide more storage space. In earlier times this method was also used as a weak copy protection for floppy disks with proprietary software, since the MS-DOS and Windows 95/98 / 98SE operating systems could not copy such floppy disks by default. Overformatting creates up to 82 tracks with up to 22 sectors per track on the floppy disk. Common oversize formats are 82 tracks with 21 sectors per track, which results in a capacity of 1,722 KB, and 80 tracks with 22 sectors per track, which results in a capacity of 1,760 KB. The latter format is even used by the AmigaOS as the standard format for HD floppy disks. For MS-DOS and Windows there are special programs for overformatting floppy disks; under Linux this is possible with the command fdformat . Overformatting, reading and writing to overformatted floppy disks does not work with all floppy disk drives, although this also depends on the degree of overformatting.