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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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