Modified Frequency Modulation

It was quickly replaced by double density floppy drives using modified frequency modulation (MFM).

ST506 used MFM (Modified Frequency Modulation) for the data encoding method.

Modified frequency modulation (MFM) controllers were the most common type in small computers, used for both floppy disk and hard disk drives.

Modified Frequency Modulation (MFM)

The command data rate is 423,75 kbit/s encoded using Modified Frequency Modulation (MFM).

The disks were Modified Frequency Modulation (MFM) coded in 512-byte sectors, and were soft-sectored.

BMC is also the original "frequency modulation" used on single-density floppy disks, before being replaced by "double-density" modified frequency modulation.

Modified frequency modulation begins to get interesting, because its special properties allow its bits to be written to a magnetic medium with twice the density of an arbitrary bit stream.

The first ST-506 disks used Modified Frequency Modulation (MFM) encoding, and transferred data at a rate of 5 megabits per second.

Miller encoding (also known as Delay encoding or Modified Frequency Modulation, and has variant Modified Miller encoding)

Its features are not fully used in order to cut costs, namely DMA transfers and support for single density discs; they were formatted as double density using modified frequency modulation.

Modified Frequency Modulation, commonly MFM, is a run-length limited (RLL) coding scheme used to encode the actual data-bits on most floppy disks.

Eventually Commodore gave in to disk format standardization, and made its last 5 -inch drives, the 1570 and 1571, compatible with Modified Frequency Modulation (MFM), to enable the Commodore 128 to work with CP/M disks from several vendors.

However most of the industry adopted a different MFM (Modified Frequency Modulation) formatting scheme at a fixed rotational speed, incompatible with Apple's own GCR with variable speed, resulting in a less-expensive drive, but with a lower capacity (720K rather than 800K).