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 magnetized data. Traditionally platters are made of a light aluminum alloy and coated with a magnetizable 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 magnetization 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 magnetized on each side, so a drive with 2 platters has 4 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.
Case Mounting Hole
Assuming that your hard drive, CD drive and zip drive are all internal IDE devices, you should jumper them all now. It is generally best (for various reasons) to connect the hard drive to the motherboard using one of the IDE cables, and hooking the zip drive and CD drive to the motherboard using the other cable. The vast majority of motherboards only have two IDE connectors, so you can only attach two IDE cables to the motherboard. Since each IDE cable can be connected to two IDE devices, most computers allow you to connect up to four IDE devices to the motherboard using those two cables.In general, there are three different settings that the jumpers can be in. The drive can be configured as Master, Slave or Cable Select. Jumper the hard drive as a Master. Usually, the jumper settings are printed on the outside of the hard drive, but you may have to consult the documentation. In the below picture, the hard drive is jumpered as Master, as shown in the upper left corner of the diagram. All IBM Deskstars have identical jumper diagrams.
Ribbon cable
A thin cable that resembles a car seat belt or duct tape. These cables are commonly the data cables used for devices such as a CD-ROM drive or a Hard disk drive. It is common for most ribbon cables found within a computer to contain a dotted stripe or line along one side of the cable, this line indicates which edge of the cable is pin one, helping the user connect the cable properly.
In addition to one edge of the cable being marked, most ribbon cables used today are also keyed, making it possible to only connect the cable one way
Tape Seal
Clean Seal Tapes are ideal for the demanding requirements of hard disk drive and related electronics manufacturing. These innovative tapes provide exceptionally low outgassing, a high level of permanence and yet are cleanly removable from most substrates.
Base Casting and Top Cover
The entire hard disk is mounted into a physical enclosure designed to protect it and also keep its internal environment separated from the outside air. This is necessary because of the requirement of keeping the internal environment free of dust and other contamination that could get between the read/write heads and the platters over which they float, and possibly lead to head crashes.
The bottom of the disk is often called the base casting, the name coming from the manufacturing process used to create the single piece of aluminum from which it is normally made. The drive mechanics are placed into the base casting, and another piece of usually aluminum is placed on top to enclose the heads and platters. A rubber gasket is placed between the base and cover to ensure a tight seal. On some drives, a metallic tape seal is applied around the perimeter of the drive to fully enclose the drive. The exact shape of the base and cover can vary significantly from drive to drive. Some models have the base flat and the cover like a bowl that goes over the contents; some are the opposite way.
MOTHERBOARD
North Bridge - The portion of a computer chipset that connects between the CPU and the major interfaces on the computer including memory, AGP port and PCI bus. It is also connected to the south bridge.
Integrated Drive Electronics (IDE) Interface:The term "Integrated Drive Electronics" (IDE) appeared in 1986, as Compac Corporation, Western Digital, and Magnetic Peripherals division of Control Data Corporation worked together to integrate a Western Digital controller chip onto a hard disk drive.
CPU socket
The term CPU socket (or CPU slot) is widely used to describe the connector linking the motherboard to the CPU(s) in certain types of desktop and server computers, particularly those compatible with the Intel x86 architecture.
AGP
Accelerated Graphics Port) A high-speed 32-bit port from Intel for attaching a display adapter to a PC. It provides a direct connection between the card and memory, and only one AGP slot is on the motherboard. AGP was introduced as a higher-speed alternative to PCI display adapters, and it freed a PCI slot for another peripheral device. The brown AGP slot is slightly shorter than the white PCI slot and is located about an inch farther back. AGP is superseded by PCI Express.
PCI
- PCI (Peripheral Component Interconnect) is an interconnection system between a microprocessor and attached devices in which expansion slots are spaced closely for high speed operation. Using PCI, a computer can support both new PCI cards while continuing to support Industry Standard Architecture (ISA) expansion cards, an older standard. Designed by Intel, the original PCI was similar to the VESA Local Bus. However, PCI 2.0 is no longer a local bus and is designed to be independent of microprocessor design. PCI is designed to be synchronized with the clock speed of the microprocessor.
SATA
(Serial ATA) A serial version of the ATA (IDE) interface, which has been the de facto standard hard disk interface for desktop PCs for more than two decades. The original Parallel ATA (PATA) interface was launched in 1986. SATA was introduced in 2002 at significantly higher speed, transferring data in each direction at 1.5 Gbps. A year later, SATA II increased speed to 3 Gbps.SATA provides a point-to-point channel between motherboard and drive rather than the master-slave architecture in the parallel technology (see IDE).
South Bridge
The Southbridge, also known as the I/O Controller Hub (ICH), is a chip that implements the "slower" capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. The southbridge can usually be distinguished from the northbridge by not being directly connected to the CPU. Rather, the northbridge ties the southbridge to the CPU.
Memory
Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.
Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.
DRAM
DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory). The two types differ in the technology they use to hold data, with DRAM being the more common type. In terms of speed, SRAM is faster. DRAM needs to be refreshed thousands of times per second while SRAM does not need to be refreshed, which is what makes it faster. DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds.
System Unit
Motherboard
A Motherboard or system board is the main printed, flat circuit board in an electronic device such as microcomputers. The board contains expansion slots (sockets) that accept additional boards (expansion Cards). In a microcomputer, the motherboard contains the microprocessor, the primary storage chips (or main memory cards), the buses, and all the chips used for controlling the peripherals.
Microprocessor
A microprocessor is a processor whose elements are miniaturized into one or a few integrated circuits contained in a single silicon microchip. It executes instructions. In a microcomputer, the central processing unit (CPU) is held on a single microprocessor. In order to function as a processor, it requires a system clock, primary storage, and power supply.Several important lines of microcomputers use some families of microprocessor chips. Intel and Motorola are the major companies that produce important microprocessors for IBM compatible and Macintosh computers.
Memory Chips
A memory chip is a chip that holds programs and data either temporarily or permanently. The major categories of memory chips are RAMs and ROMs.
System Clock
The clock is a device that generates periodic, accurately spaced signals used for several purposes such as regulation of the operations of a processor or generation of interrupts. The clock circuit uses the fixed vibrations generated from a quartz crystal to deliver a steady stream of pulses to the processor. The system clock controls the speed of all the operations within a computer.The clock speed is the internal speed of a computer. The clock speed is expressed in megahertzes (MHz). 33 MHz means 33 million cycles per second. A computer processor's speed is faster if it has higher clock speed. For example, a 100-Mhz processor is four times as fast internally as the same processor running at 25MHz.
Expansion Slots/Boards
Open/Closed architectures
o Open Architecture: This architecture is a system whose specifications are made public to encourage third-party vendors to develop add-on products for it. Most microcomputers adopt open architecture. They allow users to expand their systems using optional expansion boards.
o Closed Architecture: This is a system whose technical specifications are not made public. With a machine that has closed architecture, users cannot easily add new peripherals.
o Ports
o A port is an external connecting socket on the outside the computer. This is a pathway into and out of the computer. A port lets users plug in outside peripherals, such as monitors, scanners and printers.
o Serial Ports
o Serial ports are external I/O connectors used to attach modems, scanners or other serial interface devices to the computer. The typical serial ports use a 9-pin DB-9 or a 25-pin DB-25 connector. Serial ports transmit bits one after another on a single communications line. Serial lines frequently are used to link equipment that is not located close by.
o Parallel Ports
o Parallel ports are external I/O connectors on a computer used to hook up printers or other parallel interface devices. The parallel port uses a DB-25 connector. This port transmits several bits simultaneously. Parallel lines move information faster than serial lines do.
o Buses
o A bus is a data pathway between several hardware components inside or outside a computer. It not only connects the parts of the CPU to each other, but also links the CPU with other important hardware. The other important hardware includes memory, a disk control unit, a terminal control unit, a printer control unit, and a communications control unit. The capacity of a bus is expressed as bits. A larger capacity bus is faster in data transfer. For example, a 32-bit bus is faster than an 8-bit bus.
Keyboards
A keyboard is a series of switches connected to a microprocessor that monitors the state of each switch and initiates a specific response to a change in that state.
Types of Keyboards
101-key Enhanced keyboard
104-key Windows keyboard
Portable computers such as laptops quite often have custom keyboards that have slightly different key arrangements than a standard keyboard.
A typical keyboard has four basic types of keys:
Typing keys
Numeric keypad
Function keys
Control keys
Inside the Keyboard
The processor in a keyboard has to understand several things that are important to the utility of the keyboard, such as:
Position of the key in the key matrix
The amount of bounce and how to filter it
The speed at which to transmit the typematics
The key matrix is the grid of circuits underneath the keys. In most keyboards each circuit is broken at the point below a specific key. When a key is pressed the key bridges the gap in the circuit, allowing a tiny amount of current to flow through. The processor monitors the key matrix for signs of continuity at any point on the grid and therefore knows what key was pressed. If more than one key is pressed at the same time, the processor checks to see if that combination of keys has a designation in the character map.
If you continue to hold down a key, the processor determines that you wish to send that character repeatedly to the computer. This is known as typematics. In this process, the delay between each instance of a character can normally be set in software, typically ranging from 30 characters per second (cps) to as few as two cps.
Printer
A computer printer, or more commonly a printer, produces a hard copy (permanent human-readable text and/or graphics) of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as computer peripherals, and are attached by a printer cable to a computer which serves as a document source. Other printers, commonly known as network printers, have built-in network interfaces (typically wireless or Ethernet), and can serve as a hardcopy device for any user on the network.
Mouse
In computing, a mouse (plural mice or mouses) functions as a pointing device by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of a small case, held under one of the user's hands, with one or more buttons. It sometimes features other elements, such as "wheels", which allow the user to perform various system-dependent operations, or extra buttons or features can add more control or dimensional input. The mouse's motion typically translates into the motion of a pointer on a display.
The name mouse, coined at the Stanford Research Institute, derives from the resemblance of early models (which had a cord attached to the rear part of the device, suggesting the idea of a tail) to the common eponymous rodent.[1]
Monitor
(1) Another term for display screen. The term monitor, however, usually refers to the entire box, whereas display screen can mean just the screen. In addition, the term monitor often implies graphics capabilities.
There are many ways to classify monitors. The most basic is in terms of color capabilities, which separates monitors into three classes:
· monochrome : Monochrome monitors actually display two colors, one for the background and one for the foreground. The colors can be black and white, green and black, or amber and black.
· gray-scale : A gray-scale monitor is a special type of monochrome monitor capable of displaying different shades of gray.
· color: Color monitors can display anywhere from 16 to over 1 million different colors. Color monitors are sometimes called RGB monitors because they accept three separate signals -- red, green, and blue.
After this classification, the most important aspect of a monitor is its screen size. Like televisions, screen sizes are measured in diagonal inches, the distance from one corner to the opposite corner diagonally. A typical size for small VGA monitors is 14 inches. Monitors that are 16 or more inches diagonally are often called full-page monitors. In addition to their size, monitors can be either portrait (height greater than width) or landscape (width greater than height). Larger landscape monitors can display two full pages, side by side. The screen size is sometimes misleading because there is always an area around the edge of the screen that can't be used. Therefore, monitor manufacturers must now also state the viewable area -- that is, the area of screen that is actually used.
The resolution of a monitor indicates how densely packed the pixels are. In general, the more pixels (often expressed in dots per inch), the sharper the image. Most modern monitors can display 1024 by 768 pixels, the SVGA standard. Some high-end models can display 1280 by 1024, or even 1600 by 1200.
Another common way of classifying monitors is in terms of the type of signal they accept: analog or digital. Nearly all modern monitors accept analog signals, which is required by the VGA, SVGA, 8514/A, and other high-resolution color standards.
A few monitors are fixed frequency, which means that they accept input at only one frequency. Most monitors, however, are multiscanning, which means that they automatically adjust themselves to the frequency of the signals being sent to it. This means that they can display images at different resolutions, depending on the data being sent to them by the video adapters.
