Table of 8-inch floppy formats

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This is a table of 8-inch floppy diskette formats as introduced by IBM and DEC:

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 (data surfaces) 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) 33.333 250 250 250 500 500 500 500 500
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 N/A 26 26 26 26 26 26 26
Sector size (bytes) N/A N/A 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) 75 75 75 75 75 75 75
Sectors per track 8 26 15 8 26 15 26 15 8
Number of sectors 640 1,898 1,110 592 3,848 2,220 3,848 2,220 1,184
Sector size (bytes) 319 128 256 512 128 256 256 512 1024
Capacity Formatted (bytes) 81,664 242,944 284,160 303,104 492,544 568,320 985,088 1,136,640 1,212,416
Formatted (KiB) 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

In addition, Digital Equipment Corporation introduced their own floppy formats:

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 (KiB) 250.25 500.5
SS = Single Sided; SD = Single Density; DD = Double Density; TPI = Tracks per Inch; BPI = Bits per Inch

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