PRML


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PRML

PRML

(Partial Response Maximum Likelihood) A technique used to differentiate a valid signal from noise by measuring the rate of change at various intervals of the rising waveform. Bits generated by a modem or by reading a hard disk have uniform characteristics, whereas random noise does not. PRML uses digital signal processing (DSP) to reconstruct the data.

On magnetic disks, PRML increases the number of bits that can be recorded over earlier methods. It uses an RLL encoding sequence of 0,4,4 and provides an 8:9 ratio of user data to recorded data. See RLL.
References in periodicals archive ?
Early actions signaled that Deby, in fact, would be accountable to the few rather than the many, as he manipulated the PRML to the advantage of northern and eastern Muslims and particularly his own Zaghawa clan.
PRML technology solves this problem by first converting the analog read signal to a digital signal, then using the digital signal as the basis to recognize data bits.
These include Pivoting Optical Servo (POS) that eliminates the need for pre-formatted tape; Magneto-Resistive Cluster heads (MRC) and new high-efficiency Partial Response Maximum Likelihood (PRML) channel that deliver higher data-transfer rates and capacity; Advanced Metal Powder (AMP) media for extremely high data densities; and Positive Engagement, a robust tape-leader-buckling mechanism for high-duty-cycle automated environments.
Several new technologies, including a pivotal optical servo, PRML read channel changes and others required longer lead times to qualify and perfect before shipping into general availability.
Other features are Read-After-Write, PRML (Partial Response Maximum Likelihood), Timed Tracking, proven reliability with an installed base of over 7 million units, and a low cost of ownership--not to mention its availability via a multi-vendor approach to product development and market expansion.
A newer PRML channel improves on traditional PRML disk drive technology by bringing new levels of performance and capacity to LGMR technology and high-performance tape drives.
The EIM houses another key feature: the Advanced Partial Response Maximum Likelihood (PRML) channel.