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765 FDC
,/* MFM Encoding */
MFM, or Modified Frequency Modulation, was developed as a more efficient alternative to FM encoding. The core idea behind MFM is to reduce the number of magnetic transitions needed to represent data, thereby allowing more information to be stored in the same amount of space.
In MFM, clock pulses are not always present. Instead, a clock pulse only occurs between two consecutive 0s. If a 1 appears, it doesn’t need a clock pulse to mark it; instead, a transition is placed in the middle of the bit cell to represent the 1. Additionally, when a 0 follows a 1, no transition is needed, further minimizing the number of magnetic changes.
This method dramatically reduces the number of transitions compared to FM. Additionally, when a 0 follows a 1, no transition is needed, further minimizing MFM typically uses about half the number of magnetic changestransitions compared to FM, though the exact reduction depends on the data being encoded.
[[File:MFM encoding scheme.png|600px]]