Single density
Single Density , abbreviated to SD or 1D , is a term for the recording density on older floppy disks and magnetic tapes . The FM method is used for coding . SD disks are available in the formats 8 ", 5.25" and rarely also 3.5 "and 3". SD disks are the first generation of computer disks and came on the market in 1971 (8 ") and 1976 (5.25"). 8 "and 5.25" SD disks are available in single sided (SS) and double sided (DS) versions.
8 "SD floppy disks have a nominal capacity of 77 tracks with a track density of 48 tpi . The number of sectors and thus the capacity are variable over a wide range. The original format had a capacity of 180 KB.
5.25 "SD floppy disks have a nominal capacity of 40 tracks with 4 sectors each at a track density of 48 tpi, which corresponds to a capacity of 80 KB (one-sided) or 160 KB (two-sided). The data transfer rate is 125 kb · s - 1 .
The rare 3.5 "SD disks have nominally 40 tracks with 9 sectors each and a track density of 67.5 tpi, which corresponds to a capacity of 360 KB (two-sided).