PRML

PRML

In computer data storage, Partial Response Maximum Likelihood (PRML) is a method for converting the weak analog signal from the head of a magnetic disk or tape 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 whereas 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".

See also

* Maximum likelihood
* Viterbi algorithm
* Extended PRML

External links

* [http://www.storagereview.com/guide2000/ref/hdd/geom/dataPRML.html Storage Review: PRML]
* [http://www.guzik.com/solutions_chapter9.shtml Online Chapter "Introduction to PRML" from Alex Taratorin's book "Characterization of Magnetic Recording Systems: A Practical Approach"]


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  • PRML —   [Abk. für Partial Response Maximum Likelihood, dt. »teilweise Antwort, maximale Ähnlichkeit«], Verfahren, das die Signale des Festplatten Lesekopfs auswertet. Hierbei errechnet ein digitaler Signalprozessor (DSP), welche Daten dem gelesenen… …   Universal-Lexikon

  • PRML — Partial Response/Maximum Likelihood (PRML) ist ein Schreibverfahren, um Daten auf magnetische Datenträger zu schreiben. Um Daten auf einen magnetischen Datenträger zu schreiben, werden diese Daten vorher kodiert. Durch diesen Trick erhält man… …   Deutsch Wikipedia

  • PRML —   Sigles d’une seule lettre   Sigles de deux lettres   Sigles de trois lettres > Sigles de quatre lettres   Sigles de cinq lettres   Sigles de six lettres   Sigles de sept… …   Wikipédia en Français

  • PRML — Partial Response/Maximum Likelihood (Academic & Science » Electronics) …   Abbreviations dictionary

  • PRML — Partial Response Maximum Likelihood …   Acronyms

  • PRML — ● ►en sg. f. ►DISQUE Partial Response Maximum Likehood. Type de tête de lecture de disque dur, technologie du futur. Voir aussi MR, TF …   Dictionnaire d'informatique francophone

  • PRML — Partial Response Maximum Likelihood …   Acronyms von A bis Z

  • PRML — abbr. Partial Response Maximum Likelihood …   Dictionary of English abbreviation

  • PRML — abbr. Partial Response Maximum Likelihood (HDD) comp. abbr. Partial Response Maximum Likelihood …   United dictionary of abbreviations and acronyms

  • Extended PRML — In magnetic storage for computers,extended partial response, maximum likelihood, also known as extended PRML or EPRML, is an evolutionary improvement on the PRML design that has been developed over the last few years. The advance was the result… …   Wikipedia

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