Modified Frequency Modulation

storage (MFM, Modified FM, or sometimes "Multiple

Frequency Modulation") A modification to the original

frequency modulation scheme for encoding data on magneticdisks. MFM allows more than 1 symbol per flux transition (up

to 3), giving greater density of data. It is used with a data

rate of between 250-500 kbit/s on industry standard 3.5" and

5.25" low and high density diskettes, and up to 5 Mbit/s on

ST-506 hard disks. Except for 1.44 MB floppy disks, this

encoding is obsolete.

Other data encoding schemes include GCR, FM, RLL. See

also: PRML.

(2002-06-24)