8 inch floppy disks

Telefunken Diktatgerät (1962)

The 8" floppy disk (diskette) - the progenitor of this family of flexible magnetic media - was introduced by IBM in the late 1960's, inspired by the flexible, self-centering magnetic disk used by Telefunken in its dictation recorder [5]. The Telefunken disk was grooved like a gramophone record, and was not permanently enclosed in a jacket like the floppy disk.
ibm diskette

IBM 370/145 microcode disk (1973)

The following is mainly meant to illustrate the lack of standardization in the early use of this medium, a situation which remained until the latter days of the third (3.5") generation of floppy disks. This may be a nuisance for data archivists and computer archeologists; however standardization can also hamper the perfection of a product or idea.

A diskette is divided in tracks radially and sectors angularly. There are three ways of defining sectors: In hard disks the read/write head is automatically aligned with the tracks by a servo mechanism; in the Telefunken dictation recorder alignment is ensured by the gramophone-like grooving of the disk. In floppy drives, head positioning is done by counting steps from the predefined outer track position. Misalignment can easily happen, and is in particular a cause of trouble when diskettes are used to carry data between systems. Radial and other types of misalignment are treated in Accurite's Floppy Primer.

Originally, diskettes couldn't be protected from being accidentely erased or overwritten. Later on a write-protection notch was introduced. This notch could be closed by gluing a piece of light-tight tape over it. For compatibility reasons, it was obvious to define the open-notch situation as write-protected (later, 5.25 inch diskettes used the opposite convention). Obviously an open write-protect notch was only effective in floppy drives equipped with the appropriate optical sensor.

Details of recording formats are given in [1].


Disk formats supported by the Matrox FFD-1 Floppy disk controller [8]:

8inch formats

IBM standard format [3]

CP/M standard format [6]

Nova 3 floppy disk [4]

Digital Equipment Corp. RX01 [7]

Digital Equipment Corp. RX02 [7]

Radio Shack TRS80 Model II [9]


For extensive information about floppy disks in general, see Wikipedia: Floppy disk. Photos [EJ].


[1] J.D. Lenk: Handbook of microprocessors, microcomputers and minicomputers. Prentice-Hall 1979.
[2] Proc IEEE 74(1986) #11 , special section on magnetic information storage technology.
[3] B. Wilkinson, D. Horrocks: Computer peripherals. Hodder& Stoughton (London) 1980.
[4] Data General Diskette Subsystem 6030/31 Product Brief.
[5] E.W. Pugh e.e.: IBM's 360 and early 370 Systems MIT Press 1991.
[6] A.R. Miller: Mastering CP/M. Sybex 1983.
[7] Microcomputer interfaces handbook. DEC 1980.
[8] Matrox FFD-1 Floppy disk controller manual, 1981.
[9] TRS80 Model II Disk Operating Reference Manual, Radio Shack 1979.

rev. February, 2017