Partial Response Maximum Likelihood

storage (PRML) A method for converting the weak analog

signal from the head of a magnetic disk drive into a digital

signal. PRML attempts to correctly interpret even small

changes in the analog signal, whereas peak detection relies

on fixed thresholds. Because PRML can correctly decode a

weaker signal it allows higher density recording.

For example, PRML would read the magnetic flux density pattern

70, 60, 55, 60, 70 as binary "101", and the same for 45, 40,

30, 40, 45. A peak detector would decode everything above,

say, 50 as high, and below 50 as low, so the first pattern

would read "111" and the second as "000".

(1996-12-27)