Glossary
WD Scorpio MX375M
46
RELEASED 11/17/10 (WD CONFIDENTIAL)
2679-771293-A01
Perpendicular Magnetic Recording (PMR)
- In PMR, the magnetization of each data bit is aligned
vertically rather than longitudinally to the spinning disk. The adjacent bits attract instead of repel (as with bar
magnets placed side by side), creating more thermally stable bits.
PRML (Partial Response Maximum Likelihood)
- A read channel using sampled data, active
equalization and Veterbi detection to accurately retrieve the user data off the disk.
Reduced Power Spinup (RPS)
— WD’s optimized start up feature specifically designed for the external
hard drive and Consumer Electronics (CE) market. Specific focus for RPS is to minimize the duration and
magnitude of the peak power consumption from the hard drive.
RoHS (Restriction of Hazardous Substances)
— WD complies with the Restriction of Hazardous
Substances (RoHS) Directive 2002/95/EC of the European Parliament, which is effective in the EU beginning
July 1, 2006. RoHS aims to protect human health and the environment by restricting the use of certain
hazardous substances in new equipment, and consists of restrictions on lead, mercury, cadmium, and other
substances.
Rotational Latency
- The amount of delay in obtaining information from a hard drive that can be attributed
to the rotation of the disk.
RPM (Revolutions per Minute)
- Rotational speed of the media (disk), also known as the spindle speed.
Hard drives spin at one constant speed. The slower the RPM, the higher the mechanical latencies. Disk RPM is
a critical component of hard drive performance because it directly impacts the rotational latency of the disk
transfer rate.
Serial ATA (SATA)
- SATA is the next generation bus interface for hard drives. It is designed to replace
Parallel ATA, and has many advantages including increased transfer rate, improved signal integrity, enhanced
data protection, and hot plugging.
Sector
- A 512-byte packet of data.
Seek Time
- The time it takes for the read/write head to move to a specific block of data on the hard drive.
The average seek time is computed by dividing the time it takes to complete a large number of random seeks by
the number of seeks performed.
Self-Monitoring, Analysis, and Reporting Technology (S.M.A.R.T.)
- A technology to assist the
user in preventing possible system down time due to hard drive failure.
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.
System-on-Chip
- 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.
Thermal Asperity
- A thermal asperity is a baseline shift in the readback signal due to heating of the
magnetoresistive stripe on the head as a result of physical contact with the disk or a particle.
Unrecoverable Error
- A read error that cannot be overcome by an ECC scheme or by rereading the data
when host retries are enabled.
Write Cache
- A feature in CacheFlow that posts “command complete” prior to completing the actual write.
