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Techno
Page - By Harendra Alwis
Linux still
on top
As we
pointed out a few weeks ago, Linux continues to power its way into
the enterprise. Managing Linux-based systems is fast becoming a
top priority in corporate businesses. Linux system administration
will soon become a vital skill for IT professionals of the future.
So the message going out this week for all those aspiring to be
computer scientists and professionals in Information Technology
is a simple one: learn to talk and make friends with Linux. Learn
how to tether its power and unleash its potential. It will be a
skill that will be both essential and very useful in the near future.
Techno Page
appreciates your views and comments. Mail them in to technopage_lk@yahoo.com.
Learn
more about the hard drive
All hard
drives share a basic structure and are composed of the same physical
features. However, not all hard drives perform the same way as the
quality of the parts of the hard drive will affect its performance.
Following is a description of the common features of the hard drive
and how each part works in relation to the others. Hard drives are
extremely sensitive equipment and the internal workings of a hard
drive should not be handled by anyone other than an experienced
professional.
The platters
The platters are the actual disks inside the drive that store
the magnetised data. Traditionally, platters are made of a light
aluminum alloy and coated with a magnetisable material such as a
ferrite compound that is applied in liquid form and spun evenly
across the platter or thin metal film plating that is applied to
the platter through electroplating, the same way that chrome is
produced. Newer technology uses glass and/or ceramic platters because
they can be made thinner and also because they are more efficient
at resisting heat. The magnetic layer on the platters has tiny domains
of magnetisation that are oriented to store information that is
transferred through the read/write heads. Most drives have at least
two platters, and the larger the storage capacity of the drive,
the more platters there are. Each platter is magnetised on each
side, so a drive with two platters has four sides to store data.
The spindle
and spindle motor
The platters in a drive are separated by disk spacers and are
clamped to a rotating spindle that turns all the platters in unison.
The spindle motor is built right into the spindle or mounted directly
below it and spins the platters at a constant set rate ranging from
3,600 to 7,200 RPM. The motor is attached to a feedback loop to
ensure that it spins at precisely the speed it is supposed to.
The
read/write heads
The read/write heads read and write data to the platters. There
is typically one head per platter side, and each head is attached
to a single actuator shaft so that all the heads move in unison.
When one head is over a track, all the other heads are at the same
location over their respective surfaces. Typically, only one of
the heads is active at a time, i.e., reading or writing data. When
not in use, the heads rest on the stationary platters, but when
in motion, the spinning of the platters create air pressure that
lifts the heads off the platters. The space between the platter
and the head is so minute that even one dust particle or a fingerprint
could disable the spin. This necessitates that hard drive assembly
be done in a clean room. When the platters cease spinning the heads
come to rest, or park, at a predetermined position on the heads,
called the landing zone.
The head
actuator
All the heads are attached to a single
head actuator, or actuator arm, that moves the heads around the
platters. Older hard drives used a stepper motor actuator, which
moved the heads based on a motor reacting to stepper pulses. Each
pulse moved the actuator over the platters in predefined steps.
Stepper motor actuators are not used in modern drives because they
are prone to alignment problems and are highly sensitive to heat.
Modern hard drives use a voice coil actuator which controls the
movement of a coil toward or away from a permanent magnet based
on the amount of current flowing through it. This guidance system
is called a servo.
The platters,
spindle, spindle motor, head actuator and the read/write heads are
all contained in a chamber called the head disk assembly (HDA).
Outside of the HDA is the logic board that controls the movements
of the internal parts and controls the movement of data into and
out of the drive.
Sent in by
Viraj de Silva
History of
quantum computing
The idea of a computational device based on quantum mechanics was
first explored in the 1970s and early 1980s by physicists and computer
scientists such as Charles H. Bennett ( IBM ), Paul A. Benioff (Argonne
National Laboratory), David Deutsch (Oxford) and the late Richard
P. Feynman (Caltech). The idea emerged when scientists were pondering
the fundamental limits of computation. They understood that if technology
continued to go by the Moore's Law, then the continually shrinking
size of circuitry packed onto silicon chips would eventually reach
a point where individual elements would be no larger than a few
atoms. Here a problem arose, because at the atomic scale, the physical
laws that govern the behaviour and properties of the circuit are
inherently quantum mechanical in nature, not classical. This raised
the question of whether a new kind of computer could be devised
based on the principles of quantum physics.
In 1982, Feynman
was among the first to attempt to provide an answer to this question
by producing an abstract model in 1982 that showed how a quantum
system could be used to do computations. Then, in 1985, Deutsch
realised that Feynman's assertion could eventually lead to a general
purpose quantum computer and published a crucial theoretical paper
showing that any physical process, in principle, could be modelled
perfectly by a quantum computer. Thus, a quantum computer would
have capabilities far beyond those of any traditional classical
computer. After Deutsch published this paper, the search began to
find interesting applications for such a machine. After some years,
the next breakthrough was the invention of quantum algorithms by
Shor and Grover(as mentioned previously). With this breakthrough,
quantum computing transformed from a mere academic curiosity directly
into a national and world interest.
Sent in by
Nuwan Karunaratne
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