Disk density
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Disk density is a capacity designation on
8-inch media
Single density (SD or 1D) describes the first generation of floppy disks that use an iron oxide coating. Floppy drives utilize 300-oersted write heads, FM encoding, and a track width of 0.330 mm (0.0130 in) for a density of 48 tracks-per-inch (tpi) and 5,876 bits-per-inch (bpi).
Double density (DD or 2D) doubles capacity over SD by replacing FM encoding with an improved
5¼-inch media
SD (1D) and DD (2D) designations were generally identical to those of 8-inch disks.
Quad density (QD or 4D) doubles capacity over DD by narrowing the width of tracks to 0.160 mm (0.0063 in) for a density of 96 tpi. Some manufacturers (
The
High density (HD) improves capacity by utilizing a 96 tpi track density in conjunction with improved cobalt disk coating and stronger 600-oersted write heads, allowing 9,646 bpi to be written.
3½-inch media
Double density (DD) 3½-inch disks use an iron oxide coating, just as with 5¼-inch DD/QD disks. However, drives utilize stronger 670-oersted write heads and a narrower track width of 0.115 mm (0.0045 in) for a density of 135 tpi and 8,717 bpi.
High density (HD) 3½-inch disks switch to a cobalt disk coating, just as with 5¼-inch HD disks. Drives use 700-oersted write heads for a density of 17,434 bpi.
Extra-high density (ED) doubles the capacity over HD by using a barium ferrite coating and a special write head that allows the use of perpendicular recording.[1][2]
Triple density (TD) triples the capacity over ED by tripling the track density and improving other parameters.
Overview
| Size | 8-inch | 5¼-inch | 3½-inch | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Density | SD | DD | SD | DD | QD | HD | DD | HD | ED[1] | TD[4] | |
| Disk coating | Iron oxide[1][6] | Cobalt[1][6] | ? | Iron oxide, Cobalt?[1] | Cobalt[1][6] | Barium ferrite[1] | ? | ||||
| Coercivity [Oe] | 290,[7] 300[8][1][6] | 600,[1][6] 660,[7] 670[8] | ca. 600 | 600?,[1][6] 660,[7] 670[8] | 700,[8] 720[7][1] | 750?,[1] 1060,[7] 1200 | ? | ||||
| Coating thickness [ µm ]
|
? | ? | ? | 100,[8] 2.5,[7] 2.0-3.0[6] | ? | 55,[8] 1.3,[7] 1.0-1.5[6] | ? | 65,[8] 1.9,[7] 2.0-3.0[6] | 55,[8] 0.9,[7] 1.0-1.5[6] | ? | ? |
| Line code | FM
|
GCR
|
FM | MFM or GCR | MFM | MFM[9] | MFM or GCR | MFM | |||
| Track width [mm] | 0.330[1] | 0.160[1] | ? | 0.115[1] | ? | ||||||
| Track density [tpi] | 48[1] | 96[1] or 100 | 96[1] | 67.5[9] | 135[1] | 406.5[4] | |||||
| Bit density [bpi] | 5,876,[2][1] 5,922[10] | 9,646,[1] 9,870[2] | 8,650[9] | 8,717[2][1] | 17,432,[2] 17,434[1] | 34,868[2][1] | 36,700[4] | ||||
| Recording direction | longitudinal / horizontal[1] | perpendicular / vertical[1] | longitudinal[2] / horizontal[1] | ||||||||
See also
References
- ^ ISBN 3-89319-705-2.
- ^ Intel Corporation, IMD Marketing. AP-358, 292093-002. Archived(PDF) from the original on 2017-06-19. Retrieved 2017-06-19.
- PC88VA3eingesetzt werden. Die Laufwerke mit der Bezeichnung PC FD810.1 sind voraussichtlich ab dem vierten Quartal dieses Jahres lieferbar. Bis Ende 1989 will NEC die ersten 150000 Geräte verkauft haben. […]
- ^ NEC Corporation. October 1991. Archived(PDF) from the original on 2017-03-20. Retrieved 2017-03-20.
- ^ "PC-88VA <ハードウエア>" (in Japanese). 1995-06-24. Archived from the original on 2017-06-18. Retrieved 2017-06-18.
- ^ ISBN 0-07-041272-3.
- ^ Imation.)
- ^ a b c d e f g h Scott, Greg (1990-07-16). "More on Floppies". U-M Computing News. 5 (12). University of Michigan, Information Technology Division: 10–11. Retrieved 2017-06-19.
- ^ Epson PX-8(Geneva) CP/M laptop.)
- ^ Williams, John J. "FM vs. MFM encoding". Disk Service Manual III - Unleash the Power of Your System! (PDF) (III ed.). Alamogordo, New Mexico, USA: Consumertronics Co. Retrieved 2021-11-02.
External links
- (M)Tronics SCS (2007-05-20). "Floppy-Disketten-Laufwerke" [Floppy disk drives] (in German). Archived from the original on 2017-06-19. Retrieved 2017-06-19.