Extended Partial Response/maximum Likelyhood (EPRML) is a recording mode for data on magnetic media, mostly non removable disks.

In order to write data on the surface of such a disk memory, the oxide coating, these data are coded before by the CONTROLLER of the non removable disk, over e.g. to reach a higher data density and to embed additional technical information such as synchronisation signals into the data stream.

One of the current (2004) procedures calls itself PRML and the improved version is E PRML. Although being based on the same principle as PRML, reached by EPRML with the help of improved algorithms and better signal processing a data density higher around 20-70 per cent. These two procedures in current non removable disks apply .

Historical predecessors such as FM, MFM, GCR and RLL are not used today no more with non removable disks. One finds MFM however still on PC disks and GCR still on Commodore - (C64, C128, Amiga) and old Apple (140KB and 800KB) - disks.


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