Perpendicular Magnetic Recording (Pmr); System-On-Chip (Soc); Command Transport (Sct); Write Same - Western Digital WD15NPVX Technical Reference Manual

Product Features
To address this requirement, WD has developed Reduced Power Spinup (RPS) mode. RPS-enabled
drives use minimal power consumption during spin up, allowing a greater range of compatibility with
various systems and cables in the marketplace. RPS mode is set via jumper. See Figure 5-4 for more
information.
3.6

Perpendicular Magnetic Recording (PMR)

In perpendicular magnetic recording (PMR), the magnetization of each data bit is aligned vertically to
the spinning disk, rather than longitudinally as has been the case in hard drive technology for decades.
In longitudinal recording, as the bits become smaller and closer together, they experience an increasing
demagnetizing field, much like two bar magnets that are placed end-to-end repel one another. A
property of the media called coercivity must be increased to counteract the demagnetization to keep the
bits stable under thermal fluctuations; otherwise data corruption may occur over time. Higher media
coercivity has pushed the recording head write field to the limit of known materials.
In perpendicular recording, the adjacent bits attract instead of repel (as with bar magnets placed side by
side,) creating more thermally stable bits. In addition, the media contains a magnetically soft
underlayer (SUL) beneath the recording layer. This SUL allows a larger effective write field, thus higher
coercivity media, enabling further increases in density. Lastly, because of the vertical orientation of the
bits, the PMR recording layer tends to be thicker than that used for longitudinal recording, providing
increased signal for the read heads. All of these benefits enable WD engineers to reliably pack more data
on a given disk than is possible with conventional longitudinal recording.
3.7

System-on-Chip (SOC)

The System-on-Chip (SOC) is the foundation for WD's next generation electronics and firmware
architecture. The native SATA SOC lowers component count by integrating a hard disk controller,
high performance processor, high speed execution SRAM, and read channel in a 128-pin package. The
processor has a 5-stage pipeline which can execute instructions in a single cycle and a DSP engine for
enhanced operations. The SOC has on-chip tightly coupled memory for high speed code and data
execution that maximizes the processing bandwidth for timing critical operations. It has a high
performance disk controller that incorporates maximum flexibility, modularity, performance, and low
power consumption. The read/write channel has advanced detection capabilities for high-density
drives.
3.8 S.M.A.R.T. Command Transport (SCT)
The SCT Command Transport feature set provides a method for a host to send commands and data to
a device and for a device to send data and status to a host using log pages. Standard ATA commands
may be interspersed with SCT commands, but SCT commands cannot be nested. SCT commands that
do not require a subsequent data transfer operation are not interspersed with any ATA commands or
each other.
The SCT Command Transport feature set provides a method for a host to send commands and data to
a device and for a device to send data and status to a host using log pages. This capabilitility is used to
pass commands through a driver interface or a bridge where new or unknown commands may be
filtered and not passed to the drive. SCT is also used for issuing commands that require more than 8
parameter bytes. ATA8-ACS provides detailed information on the usage and capabilities of SCT. The
SCT feature set includes the following commands:

Write Same

Read/Write Long
Temperature Reporting
3.8.1
The Write Same command allows the host to erase the media, or write a pattern repeatedly across the
media, with a minimum of data transfer from the host. The host can clear the entire media to zeros or
14
Write Same
RELEASED 5/2/13 (WD CONFIDENTIAL)
WD Green MB500M-6Gb
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