List of floppy disk formats

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For a more in-depth textual description of some of these formats, see Floppy disk variants.

8-inch, 5+1⁄4-inch, and 3+1⁄2-inch floppy disks

This is a list of different floppy disk formats.

IBM 8-inch formats[]

This is a list of 8-inch floppy diskette formats as introduced by IBM.

Category Drive designation 23FD 33FD 43FD 53FD
Media designation N/A (read only) Type 1 Type 2 Type 2D
App. size 80 KB 242 KB 284 KB 303 KB 492 KB 568 KB 985 KB 1,136 KB 1,212 KB
Drive Heads (sides) 1 1 1 1 2 2 2 2 2
Spindle motor
speed (rpm) 		90 360 360 360 360 360 360 360 360
Controller Transfer rate (kbit/s) 33.333 250 250 250 250 250 500 500 500
Encoding FM FM FM FM FM FM MFM MFM MFM
Media Track density (tpi) 32 48 48 48 48 48 48 48 48
Bit density (bpi) 1,594 3,268 3,268 3,268 3,408 3,408 6,816 6,816 6,816
Density designation SS SD SS SD SS SD SS SD DS SD DS SD DS DD DS DD DS DD
Geometry of the
index cylinder (0) 		Sectors N/A 26 26 26 26 26 26 26
Sector size (bytes) 128 128 128 128 (side 0:128
1:256) 		(side 0:128
1:256) 		(side 0:128
1:256)
Size (bytes) N/A N/A 3,328 3,328 6,656 6,656 9,984 9,984 9,984
Geometry of
remaining cylinders 		Usable cylinders 32 73 74 74 74 74 74 74 74
Sectors per track 8 26 15 8 26 15 26 15 8
Sector size (bytes) 319 128 256 512 128 256 256 512 1024
Number of sectors 256 1,898 1,110 592 3,848 2,220 3,848 2,220 1,184
Capacity Formatted (bytes) 81,664 242,944 284,160 303,104 492,544 568,320 985,088 1,136,640 1,212,416
Formatted (KB) 79.75 237.25 277.5 296 481 555 962 1,110 1,184
SS = Single Sided; DS = Double Sided; SD = Single Density; DD = Double Density; N/A = Not Applicable; tpi = Tracks per inch; bpi = Bits per inch

DEC 8-inch formats[]

Digital Equipment Corporation used the following formats on 8-inch disks:

Category Drive designation DEC RX01 DEC RX02
App. size 250 KB 500 KB
Drive Heads (data surfaces) 1 1
Spindle motor speed (rpm) 360 360
Controller Transfer rate (kbit/s) 250 500
Encoding FM FM/MFM
Media Track density (tpi) 48 48
Bit density (bpi) 3,200 6,400
Density designation SS SD SS DD
Geometry Cylinders 77 77
Sectors per track 26 26
Total sectors per disk 2,002 2,002
Sector size (bytes) 128 256
Capacity Formatted (bytes) 256,256 512,512
Formatted (KB) 250.25 500.5
SS = Single Sided; SD = Single Density; DD = Double Density; tpi = Tracks per inch; bpi = Bits per inch

Note: "RX02 8-inch Floppy Drive Information". David Gesswein. Retrieved 2007-09-21.

The RX02 mode is not compatible with other standard drives since the headers are always in single density mode but the data is written in double density mode. Also in double density mode the standard MFM encoding was modified from the standard to prevent false header detection in data.

Other manufacturers[]

Disk Form factor[NB 1] Year introduced Formatted storage capacity
(in KB = 1024 bytes if not stated) 		Marketed capacity
IBM 23FD[1] 8-inch 1971 79.75 ?
Memorex 650[2] 8-inch 1972 175 1.5 megabit[2] unformatted
Memorex 651[3] 8-inch 1972 264 2.5 megabit[3] unformatted
IBM 33FD / Shugart 901 8-inch SSSD 1973 237.25[4][5] 3.1 Mbits unformatted
IBM 43FD / Shugart 850 8-inch DSSD 1976 500.5[6] 6.2 Mbits unformatted
Shugart SA 400 51⁄4-inch (35 track) 1976[7] 87.5[a] 110 KB
IBM 53FD / Shugart 850 8-inch DSDD 1977 980 (CP/M)-1200 (FAT) 1.2 MB
51⁄4-inch DD 1978 360 or 800 360 KB
HP single sided 31⁄2-inch 1982 280 264 KB
3-inch 1982[citation needed] 360[citation needed] ?
31⁄2-inch DD 1984 720 720 KB
51⁄4-inch QD 720 720 KB
51⁄4-inch HD 1982 YE Data YD380[9] 1200 1.2 MB
3-inch DD 1984[citation needed] 720[citation needed] ?
Mitsumi Quick Disk 3-inch 1985 128 to 256 ?
51⁄4-inch Perpendicular 1986[citation needed] 100 MB[citation needed] ?
31⁄2-inch HD 1987 1440 1.44 MB (2 MB unformatted)
31⁄2-inch ED 1987[10] 2880 2.88 MB (4 MB unformatted)
2TD drive in NEC PC-88 VA3 31⁄2-inch TD 1988 ca. 9.3 MB 12.5 MB[11] (13 MB unformatted)[12]
Fujifilm LT-1 in Zenith Minisport 2-inch 1989 ? 720 KB (245 tpi, 80 tracks/side, double-sided, double-density)
Flextra BR3020 31⁄2-inch 1990 21040 KB 21.4 MB (25 MB unformatted), double-sided, 526 cylinders × 40 sectors × 512 bytes
Floptical 31⁄2-inch 1990 20385? 21 MB,DS, 755 cylinders x 27 sectors per side x 512 bytes
Flextra BR3225 31⁄2-inch 1992? ? 50 MB unformatted, double-sided
LS-120 31⁄2-inch 1996 120.375 MB 120 MB, 1736 cylinders, 51-93 sectors, 26K to 47KB/track[13]
UHD144 31⁄2-inch 1997/1998 144 MB 144 MB, 1960 cylinders, 50-90 sectors, RLL, 281,504 sectors[14]
HiFD 150 31⁄2-inch 1998 150 MB 150 MB
HiFD 200 31⁄2-inch 1999 200 MB 200 MB
LS-240[15] 31⁄2-inch 2000/2001 240.75 MB 240 MB
Abbreviations: DD = Double density; QD = Quad density; HD = High density; ED = Extra-high density; TD = Triple-density; LS = Laser-servo; HiFD = High-capacity floppy disk;SS = Single-sided; DS = Double-sided

The formatted capacities of floppy disks is less than the unformatted capacity, which does not include the sector and track headings required for use of the disk. The amount of capacity lost to this overhead depends on the application of the drive and is beyond the manufacturer's control. Mixtures of decimal SI-style prefixes and binary record lengths required care to properly calculate total capacity. Unlike semiconductor memory, which doubled in size each time an address pin was added to an integrated circuit package and so naturally favored counts that were powers of two, the capacity of a disk drive was the product of the sector size, number of sectors per track, number of tracks per side, (and in hard drives, the number of disk platters in the drive). Individual formatted sector lengths are arbitrarily set as powers of 2 (256 bytes, 512 bytes, etc.), and disk capacity is naturally calculated as multiples of the sector size. This led to an impure combination of decimal multiples of sectors and binary sector sizes. The "1.44 MB" value for the 31⁄2-inch HD floppies is the most widely known example; where the "M" prefix is peculiar to the context of the disk drive and represents neither a decimal million nor a mebibyte 220. See Ultimate capacity and speed.

Dates and capacities marked ? are of unclear origin and need source information; other listed capacities refer to:
  • Formatted storage capacity is the total size of all sectors on the disk.
  • Marketed capacity is the capacity, typically unformatted, by the original media OEM vendor or in the case of IBM media, the first OEM thereafter.

Other formats may get more or less capacity from the same drives and disks.

Physical composition[]

Floppy disk physical characteristics
(capacity and tracks are nominal, per side)
Size Density Tracks tpi bpi Coercivity Unformatted capacity per side
21⁄2-inch[16][17] Single 16[16][17] 48[16] 64 KB[16][17]
31⁄2-inch Double[18] 40[18] 67.5[18] 8650[18] 600 Oe 250 KB
80 135 8717 600-665 Oe 500 KB
High 80 135 17434 720-750 Oe 1000 KB
Extended 80 135 34868 900 Oe 2000 KB
Triple[12] 240[11] 406.5[11] 36700[11] 6500 KB
51⁄4-inch Single/Double 40 48 5876 300 Oe 250 KB
Double 80 62.5 (Apple FileWare)
Quad 77 100 300 Oe 500 KB (Micropolis-compatible)
Quad 80 96 5922 300 Oe 500 KB
High 80 96 9646 600 Oe 833 KB
8-inch Single/Double 77 48 300 Oe 1000 KB

Logical formats[]

Throughout the 1970s and 1980s, many different logical disk formats were used, depending on the hardware platform.

Common floppy disk formats, logical characteristics by platform hide
Platform Size Density Bytes/ sector Sectors/ track Tracks/ side Sides Capacity rpm Encoding Note
Acorn 51⁄4-inch Single 256 10 40 1 100 KB 300 FM
80 200 KB
Double 256 16 40 1 160 KB MFM
80 320 KB
2 640 KB
31⁄2-inch (90 mm) Double 256 16 80 2 640 KB 300 MFM
1024 5 800 KB
High 10 1600 KB
Agat 51⁄4-inch Double 256 21 80 2 840 KB 300 MFM [NB 2]
Amstrad CPC/PCW 3-inch Single 512 9 40 1 180 KB 300 MFM Single head drive, but double-sided floppy discs (total of 360Kb per floppy)
Amstrad PCW8512/9512 3-inch Double 512 9 80 2 720 KB 300 MFM 720 KB mode uses both sides - ensure disc inserted correct way up.
Apple II 51⁄4-inch Double 256 13 35 1 113.75 KB 300 GCR [NB 3]
16 1 140 KB
31⁄2-inch (90 mm) Double 512 Variable (8-12) 80 1 400 KB 394 - 590 GCR [NB 4]
2 800 KB
High 512 18 80 2 1440 KB 300 MFM [NB 5]
Apple Lisa 51⁄4-inch FileWare Double 512 Variable (15-22) 46 2 851 KB 218 - 320 GCR
Apple Lisa 2/Macintosh XL 31⁄2-inch (90 mm) Double 512 Variable (8-12) 80 1 400 KB 394 - 590 GCR
Apple Macintosh 2 800 KB
High 512 18 80 2 1440 KB 300 MFM
Atari 8-bit 51⁄4-inch Single 128 18 40 1 90 KB 288 FM [NB 6]
Enhanced 128 26 130 KB MFM
Double 256 18 180 KB
Double 256 18 2 360 KB 300
Atari ST/TT/Falcon 31⁄2-inch (90 mm) Double 512 9 80 1 360 KB 300 MFM
2 720 KB
High 18 1440 KB
Coleco ADAM 51⁄4-inch Double 512 8 40 1 160 KB 300 MFM
Commodore (8-bit) 51⁄4-inch Double 256 Variable (17-21) ZCAV 35 1 170 KB 300 GCR [NB 7]
2 340 KB
Quad Variable (23-29) ZCAV 77 1 521 KB
2 1042 KB
31⁄2-inch (90 mm) Double 512 10 80 2 800 KB MFM  
Commodore Amiga 51⁄4-inch Double 512 11 40 2 440 KB[NB 8] 300 MFM [NB 9]
Quad 80 880 KB[NB 10]
31⁄2-inch (90 mm) Double 880 KB
High 19 1520 KB GCR [NB 11]
22 1760 KB 150 MFM [NB 9]
IBM 3740 8-inch Single 128 26 73 1 237.25 KB 360 FM [NB 12]
DEC RX50 51⁄4-inch Double 512 10 80 1 400 KB 300 MFM
IBM PC compatibles[19] 8-inch Single 128 26 77 1 250.25 KB[NB 13][19][20][21] 360 MFM [NB 14]
2 500.5 KB[NB 13][19][20][21]
Double 1024 8 1 616 KB[NB 13][20][21]
2 1232 KB[NB 13][19][20][21]
51⁄4-inch Double 512 8 40 1 160 KB[NB 13] 300 MFM  
2 320 KB[NB 13]
9 1 180 KB[NB 13]
2 360 KB[NB 13]
Quad[NB 15] 8 80 1 320 KB[NB 13] 300
2 640 KB[NB 13]
High 15 80 2 1200 KB[NB 13] 360
31⁄2-inch (90 mm) Double 512 8 80 1 320 KB[NB 13] 300 MFM
9 360 KB[NB 13]
8 2 640 KB[NB 13]
9 720 KB[NB 13]
High 18 1440 KB[NB 13]
21 1680 KB[NB 13] DMF[NB 16]
82 1720 KB[NB 13]
Extended 36 80 2880 KB[NB 13]
Platform Size Density Bytes/ sector Sectors/ track Tracks/ side Sides Capacity rpm Encoding Note
MGT SAM Coupé 31⁄2-inch (90 mm) Double 512 10 80 2 800 KB 300 MFM  
NEC PC98 8-inch Single 128 26 77 1 250.25 KB[NB 13] 360 FM  
Double 1024 8 77 2 1232 KB[NB 13] MFM
51⁄4-inch Double 512 8 80 2 640 KB[NB 13] 360 MFM
9 720 KB[NB 13]
High 15 1200 KiB[NB 13]
1024 8 77 (80)[NB 17] 1232 (1280) KB[NB 13][NB 17] [NB 17]
31⁄2-inch (90 mm) Double 512 8 80 2 640 KB[NB 13] 360 MFM
9 720 KB[NB 13]
High 15 1200 KB[NB 13] 3-mode[NB 18][NB 17]
1024 8 77 (80)[NB 17] 1232 (1280) KB[NB 13][NB 17]
512 18 80 1440 KB[NB 13] 300
Triple 512 38 240 9120 KB 360 NEC PC-88 VA3 2TD drive only[11][12]
Osborne 1[22] 51⁄4-inch Single 256 10 40 1 100 KB 300 FM
Double 1024 200 KB MFM
Sega SF-7000 3-inch Single 256 16 40 2 160 KiB ? ? Expansion unit for SC-3000 home computer. Capacity is per side.

[23]

SHARP X68000 51⁄4-inch High 1024 8 77 2 1232 KB[NB 13] 360 MFM  
31⁄2-inch (90 mm)
SHARP CE-1600F,[16] [17] 21⁄2-inch (63.5 mm)[16][17] Single (250 kbit/s, 48 tpi[16]) 512[16][17] 8[16][17] 16 (tracks 00..15)[16][17] drive: 1, diskette: 2 (turnable)[16][17] 2× 64 KB[16][17] 270[16] GCR (4/5)[16][17] Internally based on FDU-250 Micro Floppy Disk Drive Unit[16]
Thomson 51⁄4-inch Single 128 16 40 1 80 KB 300 FM Thomson UD90.070
Double 256 2 320 KB MFM Thomson DD90-320[NB 19]
31⁄2-inch (90 mm) Double 256 16 80 1 320 KB 300 MFM Thomson TO9, Thomson DD09-350
Double 2 640 KB Thomson TO8D, TO9+, Thomson DD90-352[NB 20]

See also[]

  • Zip drive (floppy-like, but incompatible medium using different technology)
  • PocketZip (floppy-like, but incompatible medium using different technology)
  • SuperDisk (floppy-like with drives also compatible with 3.5" floppy disks)

Notes[]

  1. ^ Floppy disk sizes are almost universally referred to in inch measurements, even in countries where metric is the standard, and even when the size is in fact defined in SI; for instance, the 31⁄2-inch floppy is defined as 90 mm.
  2. ^ Custom controller with unique track layout.[1]
  3. ^ 16 sector filesystems require a compatible disk controller (PROM update) and Apple DOS 3.3 or later.
  4. ^ Apple II double-density 31⁄2-inch (90 mm) drives use variable sectors sizes (tracks 00-15: 12 sectors, tracks 16-31: 11 sectors, tracks 32-47: 10 sectors, tracks 48-63: 9 sectors, tracks 64-79: 8 sectors), 394 rpm to 590 rpm. [2]
  5. ^ Apple II high-density 31⁄2-inch (90 mm) drives require a compatible disk controller and ProDOS 8.
  6. ^ Third party drives offer up to 1440 KB.
  7. ^ Commodore floppy drives used a fixed rotation speed with variable sector density (see: Zone bit recording).
  8. ^ This format was used by the Amiga 1020 external floppy drive and some third-party drives connected to the normal Amiga floppy drive bus.
  9. ^ Jump up to: a b Though the Amiga used MFM, the format places sectors too close together for a standard IBM PC compatible floppy disk controller to read (appearing as one 5632-byte physical sector per track).
  10. ^ Format used by rare third-party drives with quad density disks; such drives were usually switchable between 80-track and 40-track (A1520/PC-compatible) operation.
  11. ^ Format used by third-party gcrdisk.device driver in order to use PC-standard HD floppy drives (which rotated at a fixed 300 rpm) via the Amiga floppy drive bus. The Amiga's floppy controller could not keep up with the data rate needed for MFM recording on HD floppies without reducing rotational speed, so the third party driver used an alternate GCR mode.
  12. ^ They have 73 data tracks, 1 index track, 2 spare tracks, 1 reserved track.
  13. ^ Jump up to: a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae The calculated formatted capacity is based on FAT12 format.
  14. ^ While IBM didn't include an 8-inch floppy drive option on any of their PCs and PC DOS, MS-DOS 1.25 supported 8-inch disks and added support for higher capacities in version 2.0. MS-DOS' predecessor 86-DOS used 8-inch diskettes as well.
  15. ^ Rare format appearing on some early PC/XT clones using quad-density disks.
  16. ^ These variations are known as DMF diskettes, used for a time to pack more data on to each disk for software distribution.
  17. ^ Jump up to: a b c d e f Inner 3 tracks of 8 sectors/track format are unused.
  18. ^ The PC98 31⁄2-inch (90 mm) formats are also known as "3 Mode" floppy disks, usable on IBM PC compatibles with a 3-mode floppy drive.
  19. ^ The two sides are managed as two independent 160 KB disks
  20. ^ The two sides are managed as two independent 320 KB disks
  1. ^ Formatted with 256 byte sectors and 10 sectors per track the capacity is 89.6 Kbytes (256 × 10 × 35 = 89,600), or 87.5 KB[8]

References[]

  1. ^ Engh, James T. (September 1981). "The IBM Diskette and Diskette Drive". IBM Journal of Research and Development. 25 (5): 701–710. doi:10.1147/rd.255.0701. Archived (PDF) from the original on September 8, 2006. Retrieved July 14, 2008.
  2. ^ Jump up to: a b "Memorex 650 Flexible Disc File OEM Manual" (PDF).
  3. ^ Jump up to: a b "Memorex 651 Flexible Disc File OEM Manual" (PDF).
  4. ^ Engh, James T. (September 1981). "The IBM Diskette and Diskette Drive". IBM Journal of Research and Development. 25 (5): 701–710. doi:10.1147/rd.255.0701. Archived (PDF) from the original on September 8, 2006. The user capacity of the diskette was established at 242 944 bytes on 73 tracks with 26 sectors on each track.
  5. ^ Stevens, L. D. (1981). The Evolution of Magnetic Storage (PDF). Archived from the original (PDF) on February 26, 2020. This drive, with a capacity of 243 Kbytes.
  6. ^ Engh, James T. (1981). "The IBM Diskette and Diskette Drive" (PDF). Archived from the original (PDF) on November 27, 2007. This would double the capacity to approximately 0.5 megabytes (Mbytes).
  7. ^ Sollman, George (July 1978). "Evolution of the Minifloppy Product Family". IEEE Transactions on Magnetics. 14 (4): 160–166. doi:10.1109/TMAG.1978.1059748. In September, 1976, the first minifloppy disk drive was introduced by Shugart Associates.
  8. ^ "Shugart SA 400 Datasheet". Archived from the original on January 4, 2015.
  9. ^ 1986 Disk/Trend Report, Flexible Disk Drives
  10. ^ Mueller, Scott: "Upgrading and Repairing PCs", p. 656, Que Publishing, 2002.
  11. ^ Jump up to: a b c d e "ハードウエア" [Hardware]. NEC PC-88VA (in Japanese). Archived from the original on June 18, 2017.
  12. ^ Jump up to: a b c NEC μPD72070 - Floppy Disk Controller Specification Version 2.0 (PDF). 2.0 preliminary. NEC Corporation. October 1991. Archived from the original (PDF) on March 20, 2017. Retrieved March 20, 2017.
  13. ^ "Mass storage: basic information". MCbx Old Computer Collection. 2012.
  14. ^ "Specifications and Characteristics". SpinDisk Corporation. Archived from the original on May 5, 2003.
  15. ^ "32MB on a humble floppy". The Register. October 23, 2000.
  16. ^ Jump up to: a b c d e f g h i j k l m n o "Model CE-1600F". Sharp PC-1600 Service Manual (PDF). Yamatokoriyama, Japan: Sharp Corporation, Information Systems Group, Quality & Reliability Control Center. July 1986. pp. 98–104. Archived (PDF) from the original on March 23, 2017. Retrieved March 23, 2017.
  17. ^ Jump up to: a b c d e f g h i j k Sharp Service Manual Model CE-140F Pocket Disk Drive (PDF). Sharp Corporation. 00ZCE140F/SME. Archived (PDF) from the original on March 11, 2017. Retrieved March 11, 2017.
  18. ^ Jump up to: a b c d http://electrickery.xs4all.nl/comp/px8/doc/PF-10Manual.pdf Epson PF-10 Manual for PX-8
  19. ^ Jump up to: a b c d "Standard Floppy Disk Formats Supported by MS-DOS". 2.0. Microsoft. December 17, 2000. Retrieved February 5, 2020.
  20. ^ Jump up to: a b c d Zbikowski, Mark; Allen, Paul; Ballmer, Steve; Borman, Reuben; Borman, Rob; Butler, John; Carroll, Chuck; Chamberlain, Mark; Chell, David; Colee, Mike; Courtney, Mike; Dryfoos, Mike; Duncan, Rachel; Eckhardt, Kurt; Evans, Eric; Farmer, Rick; Gates, Bill; Geary, Michael; Griffin, Bob; Hogarth, Doug; Johnson, James W.; Kermaani, Kaamel; King, Adrian; Koch, Reed; Landowski, James; Larson, Chris; Lennon, Thomas; Lipkie, Dan; McDonald, Marc; McKinney, Bruce; Martin, Pascal; Mathers, Estelle; Matthews, Bob; Melin, David; Mergentime, Charles; Nevin, Randy; Newell, Dan; Newell, Tani; Norris, David; O'Leary, Mike; O'Rear, Bob; Olsson, Mike; Osterman, Larry; Ostling, Ridge; Pai, Sunil; Paterson, Tim; Perez, Gary; Peters, Chris; Petzold, Charles; Pollock, John; Reynolds, Aaron; Rubin, Darryl; Ryan, Ralph; Schulmeisters, Karl; Shah, Rajen; Shaw, Barry; Short, Anthony; Slivka, Ben; Smirl, Jon; Stillmaker, Betty; Stoddard, John; Tillman, Dennis; Whitten, Greg; Yount, Natalie; Zeck, Steve (1988). "Technical advisors". The MS-DOS Encyclopedia: versions 1.0 through 3.2. By Duncan, Ray; Bostwick, Steve; Burgoyne, Keith; Byers, Robert A.; Hogan, Thom; Kyle, Jim; Letwin, Gordon; Petzold, Charles; Rabinowitz, Chip; Tomlin, Jim; Wilton, Richard; Wolverton, Van; Wong, William; Woodcock, JoAnne (Completely reworked ed.). Redmond, Washington, USA: Microsoft Press. ISBN 1-55615-049-0. LCCN 87-21452. OCLC 16581341. (xix+1570 pages; 26 cm) (NB. This edition was published in 1988 after extensive rework of the withdrawn 1986 first edition by a different team of authors. [3])
  21. ^ Jump up to: a b c d Xerox 16/8 Professional Computer – MS-DOS OS Handbook for 8" Floppy Disks (PDF). Xerox. November 1983.
  22. ^ Hogan, Thom; Iannamico, Mike (1982). Osborne 1 Technical Manual. Osborne Computer Corporation. p. 39.
  23. ^ "Sega SF-7000 Super Control Station User Guide". Sega Enterprises. Retrieved February 10, 2020.

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