Hardware
All the elements that go together to make up a PC fall into one of two categories, hardware or software. This section is about hardware, the stuff upon which software runs.
One of the definitions of 'hardware' according to Webster's dictionary is 'major items of equipment or their components used for a particular purpose'.
This following list represents a basic set of hardware found in most PCs.
For more information on these components just click one.
-
PC Case -
MotherBoard -
Power Supply -
Hard Disk Drive(HDD) -
Floppy Disk Drive(FDD) -
Compact Disk Drive(CDD) -
Digital Disk Drive(DVD) -
Monitors (CRT and LCD) -
-
Mouse -
Audio -
PC Case
The PC case is a thin sheet metal enclosure that houses the motherboard, power supply and various drives (HDD, FDD, CD, DVD).
- Cases are offered in two styles, desktop and tower. Today the tower type is predominant. It stands upright and is much taller than it is wide. It is usually placed on the floor next to, or under a desk. The desktop has a pizza box profile and usually sits on the desktop.
- Tower cases are offered in two basic sizes, one that can fit ATX (12" wide) motherboards and one that can accommodate ATX mini (8.5" wide) motherboards. The number of drive bays offered also varies depending on manufacturer.
- The motherboard and power supply mount to the floor at the rear of the case. The drives (hard, floppy and CD/DVD) mount in enclosures called drive bays at the front of the case.
- Cases run from $20 to $70 depending on size (ATX or ATX mini), number of drive bays and the wattage of the power supply.
Motherboard
The motherboard is the main circuit board in a PC. It contains all the circuits and components that run the PC.
Major Components found on the motherboard are:
Major Components found on the motherboard are:
- CPU - the Central Processing Unit is often an Intel Pentium or Celeron processor. It is the heart of every PC. All scheduling, computation and control occurs here.
- BIOS - Basic Input Output System is a non-volatile memory that contains configuration information about the PC. It contains all the code required for the CPU to communicate with the keyboard, mouse video display, disk drives and communications devices.
When a PC is powered on it uses the BIOS 'boot code' to set up many required functions that bring the PC to a point where it is ready to work.
- RTC - the Real Time Clock chip keeps date, day and time in a 24 hour format just like your watch. The PC uses this clock to 'time stamp' files as they are created and modified. When you print a file it time stamps the pages as they are printed.
- Chip Set - these are large chip(s) that integrate many functions that used to be found in separate smaller chips on the motherboard. They save space and cost.
The functions performed by these chip sets often broken into two devices with one providing an interface from the CPU to the memory and the other providing controllers for IDE, ISA, PCI and USB devices (see below).
- Power - A 20 pin connector accepts a plug from the power supply. This plug carry DC power to all the circuits on the motherboard.
- Keyboard - A Mini-din 6-pin (round) connector found at the back of the motherboard is where the keyboard plugs in.
- Mouse - A Mini-din 6-pin connector found next to the keyboard connector is where the where the mouse plugs in.
- Display - This connector is not integrated into the motherboard but is included in this list since its function is absolutely necessary. It is a 15-pin, D-shell type connector found on a video card that plugs into the AGP connector of the motherboard (see below).
- IDE - stands for Integrated Drive Electronics. These are 40 pin connectors that provide a place to connect the ribbon cables from the drives (hard and CD/DVD). All data between the motherboard and the drives is carried in these cables. They are not accessible unless the PC cover is removed.
- FDD connector - it is similar in function to the IDE connector. It is a 34 pin ribbon connector that carries data between the motherboard and any floppy drive installed in the PC. Not accessible with PC cover on.
- DRAM - Dynamic Random Access Memory connectors for SIMM and DIMM type memory modules. Not accessible with chassis cover on.
- Serial Connectors
- Standard Serial Connector - This connector has been around in PCs since they first appeared. It was originally located on ISA expansion type cards (see below). Today it is an integral part of newer motherboards. It is a 9- pin, D-shell connector that allows you to connect external devices with serial ports to your PC. The maximum data rate is 115 KB/s.
- USB - Universal Serial Bus This is a relatively new serial bus. Originally specified as low speed, 1.2 Mb/s, it was enhanced to full speed, 12Mb/s. The latest version 2.0 is specified as high speed, 400 MB/s.
Someday USB will completely replace the standard serial connector that has been the workhorse serial port in earlier PCs. USB is now a standard connector on all new motherboards.
Unlike serial and parallel ports, the USB port is designed to power devices connected to it. The devices must be low power devices and must be able to reduce their current draw to less than 0.5uAmps when commanded to do so by the PC.
- Standard Serial Connector - This connector has been around in PCs since they first appeared. It was originally located on ISA expansion type cards (see below). Today it is an integral part of newer motherboards. It is a 9- pin, D-shell connector that allows you to connect external devices with serial ports to your PC. The maximum data rate is 115 KB/s.
- Parallel Connectors
- Centronix or Standard Parallel - This connector has been around in PCs since they first appeared. It has 37-pins and is now integrated on new motherboards. It is usually used to connect your printer to the PC and moves data at about 1MB/s.
- SCSI - Small Computer System Interface moves data at a maximum of up to 80Mb/s. It not integrated into most PC motherboards. It can be added to a PC as an Expansion card (see below). Some printers and hard disk drives use SCSI interfaces.
- Centronix or Standard Parallel - This connector has been around in PCs since they first appeared. It has 37-pins and is now integrated on new motherboards. It is usually used to connect your printer to the PC and moves data at about 1MB/s.
- Expansion Card Connectors - The CPU connects to expansion card connectors through one of the chip set ICs mentioned above. They are located on the motherboard near the rear of the PC. These connectors allow special function cards to plug into and work with the PC.
Before motherboards integrated the serial and centronix connectors they were found on expansion boards that plugged into ISA slots.
Most PCs have the following expansion connector types:
- ISA - Industry Standard Architecture connectors have been around since 1980 and first appeared in the IBM XT PC. This type of slot still appears on some newer motherboards so that older expansion boards can still be used. However, many motherboards no longer have ISA connectors on them.
- PCI - Peripheral Component Interconnect is a newer and faster interface that accepts all expansion cards that have a PCI interface.
- AGP - Accelerated Graphics Port is a connector that is designed to work with video cards. Your video display plugs into and is controlled by one of these video cards. Many modern video cards offer enhanced 3D-graphics and fast, full motion video.
- ISA - Industry Standard Architecture connectors have been around since 1980 and first appeared in the IBM XT PC. This type of slot still appears on some newer motherboards so that older expansion boards can still be used. However, many motherboards no longer have ISA connectors on them.
Power Supply
- A power supply is installed in the back corner of the PC case, next to the motherboard.
- It converts 120vac (standard house power) into DC voltages that are used by other components in the PC.
- A 20 conductor cable carries +5vdc, -5vdc +12vdc, -12vdc and ground to the motherboard.
- Another pair of cables, each with four conductors and two 4-pin connectors daisy-chained along it, carry +5vdc, +12vdc and ground to the drives (hard, floppy and CD/DVD).
- Typical PC power supplies are rated at 200-250 watts and sell for about Rs.400 – Rs.450. Higher wattage supplies are available.
Hard Disk Drive
- The HDD installs in one of the 3-1/2 inch internal drive bays in the PC. It is secured by machine screws.
- It is powered by a 4 conductor cable coming from the power supply.
- Data to and from the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
- Data is stored magnetically on multiple rigid disks that are stacked up like pancakes. Small arms with magnetic pickups move rapidly back and forth across the top and bottom surface of each disk in the drive. The sensors float just a few microns above the rotating disk surface and can read and write data at very high rates.
- Most commercially available hard drives rotate at 5400 or 7200 RPM (revolutions per minute) which translates to 90 or 120 revolutions per second respectively. The data transfer rate from the drive to the motherboard is 33 Mbytes/second in bursts. Newer drives are capable of higher speeds up to 66 Mbytes/sec. To use this faster drive, the PC must have an ATA/66 interface that is capable of keeping up with it.
- A 40 Gbyte HDD sells for about $100.
Floppy Disk Drive
- The FDD installs in one of the external drive bays at the front of the PC case and is secured by machine screws. External means you can access the drive from the outside.
- It is powered by a cable with a 4-pin connector that comes from the power supply.
- It transfers data to and from the motherboard by means of a 34 pin ribbon cable.
- It stores data magnetically on a removable floppy disk. A pickup arm in the drive floats above the disk surface. The arm moves rapidly back and forth across the disk surface as a small magnetic sensor at the end of the arm reads and writes data on the rotating disk surface.
- Floppy disks hold 1.44 Mbytes, which at one time was a large amount of data. Today many programs and files are much larger than this. In spite of being surpassed in size by CD and DVD, floppy drives are still found on many newer PCs.
- They cost about $20-$25.
Compact Disk Drive
- The CDD installs in one of the external 5-1/4 inch drive bays in the front of the PC case. It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on the CDD. These allow the drive to be removed from the PC without having to remove any screws.
- Data is stored optically on the surface of the disk. A laser attached to an arm that moves back and forth across near the disk surface and sends light toward the disk surface which is coated with of a thin layer of aluminum.
- Smooth areas called a lands reflect the light back to a photo diode located near the laser. The reflected light is read as a 1. Areas called pits are where the aluminum has been removed. When the laser light hits these, it is scattered and very little is picked up by the photo diode. The absence of light is read as a 0.
- CDD have become the predominant removable storage media for PCs and can store 700 Mbytes of data.
- A 4-pin cable from the power supply plugs into the CDD and provides power to it.
- Data to and from the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
- There are two types of Compact Disk drives available for PCs.
- CD-ROM (read only memory) is the older type. As the title implies it can only read CDs. It can read any standard CD and most CD-R type disks. It may be able to read some types of CD-RW disks too. A 24x CD-ROM unit costs about $30.
- CD-RW (ReWritable)units can read and write CD-R and CD-RW type disks. It can also read standard CD type disks.
A 24x10x40 CD-RW unit costs about $115. The 24x10x40 means the unit can write at 24x, re-write at 10x and read at 40x, where x is 150Kbytes/sec.
- CD-ROM (read only memory) is the older type. As the title implies it can only read CDs. It can read any standard CD and most CD-R type disks. It may be able to read some types of CD-RW disks too. A 24x CD-ROM unit costs about $30.
Digital Video Disk drive
- DVD also known as the Digital Versatile Disk drive, installs in one of the external 5 1/4 inch drive bays in the PC. It is secured by machine screws. Some manufacturers offer special rail-like systems that mount on the DVD. These allow the drive to be removed from the PC without having to remove screws.
- It is designed to optically access data stored on a DVD. A laser moves back and forth near the disk surface and accesses data at a very fast rate.
- A 4-pin cable from the power supply plugs into the CDD and provides power to it.
- Data between the DVD drive and the motherboard is carried on a 40-pin IDE (Integrated Drive Electronics) cable.
There are two types of DVD drives that typically go into PCs.- DVD-ROM (Read Only Memory) can read DVDs and CDs and costs about $75.
DVD-RAM (Random Access Memory) units can read and write DVDs. They can also read CDs and cost about $500.
- DVD-ROM (Read Only Memory) can read DVDs and CDs and costs about $75.
- A standard DVD stores up to 4.7 Gbytes on one side of the disk. Digitally formatted movies can be stored on a standard DVD in MPEG-2 format.
CRT Monitors
- Up until recently, CRTs (Cathode RayTubes) were the only type of displays for use with desktop PCs. They are relatively big (14" to 16" deep) and heavy (over 15 lbs).
- They are available in screen sizes from 14" to 21". A 17" display means that it is 17" measured diagonally from one corner of the tube to the other. The actual viewing area is smaller than 17" (about 16") since the electron gun can't sweep completely to the tube edge.
- CRTs send a stream of electrons at the screen, which is charged to about 25,000 volts. As they strike it they cause phosphor on the backside of the screen to glow creating light which you see. The electron stream is sweep back and forth and up and down at about 60 sweeps per second and turned off and on at the right time to make text and graphics images appear.
- They are powered by standard 120Vac wall power.
- Data is transferred to the display on a cable with a 15-pin D-shell connector that plugs into a connector on the video card which in turn plugs into one of the PC's expansion slots.
- A 17" monitor with 1280 x 1024 resolution and .27mm dot pitch sells for around $150.
LCD Monitors
- Liquid Crystal Display (LCD) technology has been used in laptops for some time. It has recently been made commercially available as monitors for desktop PCs.
- LCDs have no electron gun and are therefore not very deep like CRTs. The text and images you see are created by a back light behind the panel, that shines through pixels (picture elements). Each pixel is made up of three chambers red, green and blue. The chambers in each pixel must be opened enough and in the proper proportion to produce the correct brightness and color.
- For an LCD to provide a screen resolution 1024 x 768 pixels (SVGA), it must have 786,432 (1024 x 768) pixels. In TFT (Thin Film Transistor) type LCDs, each pixel is controlled by a tiny transistor that opens and closes the chambers in each pixel.
- Desk top LCD displays are powered by standard 120Vac wall power.
- Data is transferred to the display on a cable with a 15-pin connector that plugs into a mating connector on the video card seated in an expansion slot in the PC.
- A 17" LCD monitor with 1280 x 1024 resolution and .27mm dot pitch sells for around $500.
Keyboard
- The keyboard was the first input device developed for the PC.
- The standard keyboard layout provides 104 keys organized as four groups:
alphanumeric keys (A-Z, 0-9)
location keys (home, end etc.)
numeric keypad
function keys (F1-F12)
- In addition to the standard keys, some keyboards offer functions such as volume control for speakers, web browser functions and power management.
- Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs into the back of the motherboard.
- Standard keyboards sell for $7 to $30 depending on the feature set.
- There are wireless keyboards that communicate with a pod that is plugged into the keyboard port. Radio Frequency (RF) or InfraRed (IR) technology is used to communicate between the keyboard and the receiver pod, which plugs into the PC. Wireless keyboards are priced in the $40 to $45 range.
- Cherry Hill Inc. is releasing a keyboard that has an integrated Finger Tip sensor. Instead of having to type in passwords to access the PC a successful fingerprint match allows entry in to the PC or specific programs.
Mouse
The mouse is the most common 'pointing device' used in PCs. Every mouse has two buttons and most have one or two scroll wheels.
- By default the left button is used to select items. The right button is assigned as a context or alternate menu. A single wheel is normally set to scroll up and down on the active page . If a second wheel is present, it is usually assigned to scroll left and right on the page.
- The button functions can be reassigned by going to Control Panel > Mouse > Buttons tab.
- Data is transferred to the PC over a short cable with a circular 6-pin Mini-din connector that plugs into the back of the motherboard. This type of mouse sells for $10 to $25 depending on the style, button and wheel configuration.
- Some versions of the mouse are wireless. They communicate with a receiver pod that is plugs into the mouse port. Radio Frequency (RF) or InfraRed (IR) technology is used for communication between the mouse and the pod. These sell in the $30 to $45 range.
There are two designs used in a mouse for detecting motion:
Track ball
This type of mouse uses a rolling (track) ball. As the mouse moves the ball rolls. The rolling motion is converted electronically into matching movements of the mouse pointer that moves across your video display.
The track ball mouse is rapidly becoming another casualty of rapidly changing technology. The optical mouse has pretty much replaced it. The track ball mouse is already becoming a thing of the past.
Optical
This mouse uses an InfraRed transmitter/receiver pair to optically detect the motion of the mouse. It has a number of advantages over the track ball mouse:
No mouse pad is required.
Can work on any flat surface- No rolling track ball that collects and transfers dirt to the internal rollers, making them slip. When they do, your mouse pointer jumps around in an unpredictable and annoying way!
See the Easy Tips section of this web site for an explanation on how to clean a track ball mouse.
Audio
- Speakers and headphones are the primary audio output devices for a PC.
- Some monitors have speakers built into their sides. Other speakers are free standing.
- Passive speakers plug into and are powered directly from the output signal provided by the 'speaker out' port on the sound card.
- Active speakers amplify the sound signal from the sound card using battery or rectified AC house power.
Cables and Wires
- Although these are not the most sophisticated part of the system, they are just as important as any other component.
- All the components in a PC are connected together and to power with wires and cables.
- Ninety percent of all electronics problems (including PCs) are the result of poor connections.
- If you have a PC problem, it is always a good idea to first check that all the cables on your PC are plugged in and properly seated.
No comments:
Post a Comment