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.
TTTTT
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.
UUUUU
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.
V
VV
VV
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.
W
W
W
W
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.
