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GLOSSARY
GL – 8
strobe offset signal
A group of digital input signal levels which cause the
read PLL and/or data decoder to shift the decoding
windows by fractional amounts. Often early/late are
modified when two signals are used.
TT
TT
T
thin-film head
A magnetic transducer manufactured by deposition of
magnetic and electrical materials on a base material
contrasted with prior art mechanical methods. Read/write
heads whose read/write element is deposited using
integrated circuit techniques rather than being manually
wound.
thin-film media
See plated thin film media.
track
One surface of a cylinder. A path which contains
reproducible information left on a magnetic medium by
recording means energized from a single channel.
track-following servo
A closed-loop positioner control system that continuously
corrects the position of the disk drive’s heads by utilizing
a reference track and a feedback loop in the head
positioning system. (See also closed loop.)
tracks per inch (TPI)
A measurement of radial density. Tracks per inch of disk
radius.
track positioning
The method, both mechanical and electrical, used to
position the heads over the correct cylinder in a disk
drive system.
UU
UU
U
un-correctable error
An error that is not able to be overcome with Error
Detection and Correction.
unformatted capacity
Storage capacity of disk drive prior to formatting; also
called the gross capacity. (See format.) The raw capacity
of a drive not taking into account the capacity loss due to
storage of the format control information on the disk
surfaces.
unrecoverable error
A read error falling outside the capability of an ECC
mechanism to correct, or not able to be overcome by
rereading the data in question, with or without
repositioning the head.
VV
VV
V
voice coil motor
A positioning motor that uses the same principle as a
voice coil in a loudspeaker. The motor has no detent
positions. The mechanical motion output of it can be
either rotary or linear.
WW
WW
W
Whitney head
A successor to the original Winchester read/write head
design. The primary change was to make the flexure
smaller and more rigid. First used in IBM 3370/3380.
Whitney technology
A method of constructing a read/write head in a rigid disk
drive using a Whitney head. In all other details it is the
same as Winchester technology.
Winchester head
The read/write head used in Winchester technology,
non-removable media disk drives. May be either a
monolithic or composite type. It is aerodynamically
designed to fly within microinches of the disk surface.
Winchester technology
A method of constructing a rigid disk drive using
concepts introduced in the IBM model 3340 disk drive.
The primary changes from prior technology was to lower
the mass of the slider, use of a monolithic slider, radically
changing the design of the flexure and having the slider
come to rest on a lubricated disk surface when disk
rotation ceases. In addition to the above, a totally sealed
chamber containing the read/write heads and disks was
used to protect against contamination.
window margin
The amount of tolerance a read/write system has for
transition jitter at a specified error rate level.
word
A number of bits, typically a multiple of eight, processed
in parallel (in a single operation). Standard word lengths
are 8, 16, 32 and 64 bits (1, 2, 4, or 8 bytes).
write
The recording of flux reversals on a magnetic media.
write pre-compensation
The intentional time shifting of write data to offset the
effects of bit shift in magnetic recording.
write gate signal
A digital input signal level which causes the drive circuitry
to record (write) data.