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									   A motherboard by itself is useless, but a computer has to
    have one to operate. The motherboard's main job is to hold
    the computer's microprocessor chip and let everything else
    connect to it. Everything that runs the computer or
    enhances its performance is either part of the motherboard
    or plugs into it via a slot or port.
   The shape and layout of a motherboard is called the form
    factor. The form factor affects where individual
    components go and the shape of the computer's case.
    There are several specific form factors that most PC
    motherboards use so that they can all fit in standard cases.




Motherboards
   The form factor is just one of the many standards that apply to
    motherboards. Some of the other standards include:
    ◦ The socket for the microprocessor determines what kind of Central Processing
      Unit (CPU) the motherboard uses.
    ◦ The chipset is part of the motherboard's logic system and is usually made of two
      parts -- the northbridge and the southbridge. These two "bridges" connect the
      CPU to other parts of the computer.
    ◦ The Basic Input/Output System (BIOS) chip controls the most basic functions of
      the computer and performs a self-test every time you turn it on. Some systems
      feature dual BIOS, which provides a backup in case one fails or in case of error
      during updating.
    ◦ The real time clock chip is a battery-operated chip that maintains basic settings
      and the system time.




Motherboards
   The slots and ports found on a motherboard include:
    ◦ Peripheral Component Interconnect (PCI)- connections for video, sound and video
      capture cards, as well as network cards
    ◦ Accelerated Graphics Port (AGP) - dedicated port for video cards.
    ◦ Integrated Drive Electronics (IDE) - interfaces for the hard drives
    ◦ Universal Serial Bus or FireWire - external peripherals
    ◦ Memory slots
   Some motherboards also incorporate newer technological
    advances:
    ◦ Redundant Array of Independent Discs (RAID) controllers allow the computer to
      recognize multiple drives as one drive.
    ◦ PCI Express is a newer protocol that acts more like a network than a bus. It can
      eliminate the need for other ports, including the AGP port.
   Rather than relying on plug-in cards, some motherboards have
    on-board sound, networking, video or other peripheral support.




Motherboards
   The first microprocessor to make it into a home computer
    was the Intel 8080, a complete 8-bit computer on one chip,
    introduced in 1974. The first microprocessor to make a real
    splash in the market was the Intel 8088, introduced in
    1979 and incorporated into the IBM PC (which first
    appeared around 1982). If you are familiar with the PC
    market and its history, you know that the PC market
    moved from the 8088 to the 80286 to the 80386 to the
    80486 to the Pentium to the Pentium II to the Pentium III
    to the Pentium 4. All of these microprocessors are made by
    Intel and all of them are improvements on the basic design
    of the 8088. The Pentium 4 can execute any piece of code
    that ran on the original 8088, but it does it about 5,000
    times faster!



Processors
Name          Date   Transistors Microns   Clock speed Data width   MIPS

8080          1974   6,000        6        2 MHz      8 bits        0.64

                                                      16 bits
8088          1979   29,000       3        5 MHz                    0.33
                                                      8-bit bus

80286         1982   134,000      1.5      6 MHz      16 bits       1
80386         1985   275,000      1.5      16 MHz     32 bits       5

80486         1989   1,200,000    1        25 MHz     32 bits       20


                                                      32 bits
Pentium       1993   3,100,000    0.8      60 MHz                   100
                                                      64-bit bus


                                                      32 bits
Pentium II    1997   7,500,000    0.35     233 MHz                  ~300
                                                      64-bit bus


                                                      32 bits
Pentium III   1999   9,500,000    0.25     450 MHz                  ~510
                                                      64-bit bus


                                                      32 bits
Pentium 4     2000   42,000,000   0.18     1.5 GHz                  ~1,700
                                                      64-bit bus


Pentium 4                                             32 bits
              2004   125,000,000 0.09      3.6 GHz                  ~7,000
"Prescott"                                            64-bit bus
• The date is the year that the processor was first introduced. Many processors are
re-introduced at higher clock speeds for many years after the original release date.
• Transistors is the number of transistors on the chip. You can see that the number
of transistors on a single chip has risen steadily over the years.
• Microns is the width, in microns, of the smallest wire on the chip. For comparison,
a human hair is 100 microns thick. As the feature size on the chip goes down, the
number of transistors rises.
• Clock speed is the maximum rate that the chip can be clocked at. Clock speed will
make more sense in the next section.
• Data Width is the width of the ALU. An 8-bit ALU can add/subtract/multiply/etc.
two 8-bit numbers, while a 32-bit ALU can manipulate 32-bit numbers. An 8-bit ALU
would have to execute four instructions to add two 32-bit numbers, while a 32-bit
ALU can do it in one instruction. In many cases, the external data bus is the same
width as the ALU, but not always. The 8088 had a 16-bit ALU and an 8-bit bus, while
the modern Pentiums fetch data 64 bits at a time for their 32-bit ALUs.
• MIPS stands for "millions of instructions per second" and is a rough measure of the
performance of a CPU. Modern CPUs can do so many different things that MIPS
ratings lose a lot of their meaning, but you can get a general sense of the relative
power of the CPUs from this column.
                 What's a Chip?
 A chip is also called an integrated
  circuit. Generally it is a small, thin piece
  of silicon onto which the transistors
  making up the microprocessor have been
  etched. A chip might be as large as an
  inch on a side and can contain tens of
  millions of transistors. Simpler processors
  might consist of a few thousand
  transistors etched onto a chip just a few
  millimeters square.
Intel Processors Power Consumption
  Model     Clock Speed   Power
                                           Model            Clock Speed   Power(TDP)
  Pentium   75 Mhz        8.0 W    Pentium II Mobile        233 MHz       9W

  Pentium   90 Mhz        9.0 W    Pentium II Mobile        266 MHz       9.8 W

  Pentium   100 Mhz       10.1 W   Pentium II               233 MHz       34.8 W

  Pentium   120 Mhz       11.9 W   Pentium II (Deschutes)   266 MHz       16.8 W

                                   Pentium II (Klamath)     266 MHz       38.6 W
  Pentium   133 Mhz       11.2 W
                                   Pentium II (Klamath)     300 MHz       43.0 W
  Pentium   150 Mhz       11.6 W
                                   Pentium II (Deschutes)   400 MHz       24.3 W
  Pentium   166 Mhz       14.5 W
                                   Pentium II               450 MHz       27.1 W
  Pentium   200 Mhz       15.5 W
 Intel Processors Power Consumption
          Model         Clock Speed   Power (TDP)          Model      Clock Speed     Power
Pentium III             450 MHz       25.3 W
                                                    Pentium 4-C    2.4 GHz          67.6 W
Pentium III             500 MHz       28.0 W
Pentium III-E           500 MHz       13.2 W        Pentium 4 HT   3.06 GHz         81.8 W
Pentium III-(B)         600 MHz       34.5 W
Pentium III-E(B)        600 MHz       15.8 W        520J           2.8 GHz          84 W

Pentium III             700 MHz       18.3 W
                                                    560J           3.6 GHz          115 W
Pentium III             733 MHz       19.1 W
Pentium III             850 MHz       25.7 W
Pentium III             866 MHz       26.1 W
Pentium III (SECC2)     933 MHz       25.5 W
Pentium III (FC-PGA)    933 MHz       24.5-28.3 W
Pentium III (FC-PGA)    1000 MHz      26.1 W
Pentium III (FC-PGA2)   1000 MHz      29.0 W
Pentium III (FC-PGA2)   1200 MHz      29.9 W
Pentium III (FC-PGA2)   1266 MHz      29.5 W
Pentium III (FC-PGA2)   1400 MHz      31.2 W
Intel Processors Power Consumption

          Model         Clock Speed     Power
       E6700      2.66 GHz            65 W
       E6600      2.40 GHz            65 W
       E6400      2.13 GHz            65 W
       E6300      1.86 GHz            65 W
       E4300      1.80 GHz            65 W
       X6800      2.93 GHz            75 W
       T7600      2.33 GHz            34 W
       T7400      2.17 GHz            34 W
       T7200      2.00 GHz            34 W
       T5600      1.83 GHz            34 W
       T5500      1.67 GHz            34 W
       L7400      1.50 GHz            17 W
       L7200      1.33 GHz            17 W
       U7600      1.20 GHz            10 W
       U7500      1.06 GHz            10 W
                       Model              L2 Cache        Voltage       Power

Windsor Athlon 64 X2 3600+                512 KB                       89 W

Brisbane Athlon 64 X2 3600+ EE            512 KB     1.35 V            65 W

Windsor Athlon 64 X2 3800+                1 MB       1.20 - 1.25 V     89 W

Windsor Athlon 64 X2 3800+ EE             1 MB       1.20 - 1.25 V     65 W

Windsor Athlon 64 X2 3800+ EE SFF         1 MB       1.025 - 1.075 V   35 W

Windsor Athlon 64 X2 3800+                1 MB       1.30 - 1.35 V     89 W

Brisbane Athlon 64 X2 4000+               1 MB       1.25 - 1.35 V     65 W

Windsor Athlon 64 X2 4200+ EE             1 MB       1.20 - 1.25 V     65 W

Windsor Athlon 64 X2 4200+                1 MB       1.30 - 1.35 V     89 W

Manchester Athlon 64 X2 4200+ and below   1 MB       1.35 V            89 W

Brisbane Athlon 64 X2 4400+               1 MB       1.25 - 1.35 V     65 W

Toledo Athlon 64 X2 4400+                 2 MB       1.35 V            89/110W

Windsor Athlon 64 X2 4600+ EE             1 MB       1.20 - 1.25 V     65 W

Windsor Athlon 64 X2 4600+                1 MB       1.30 - 1.35 V     89 W

Manchester Athlon 64 X2 4600+             1 MB       1.35 V            110 W

Brisbane Athlon 64 X2 4800+               1 MB       1.25 - 1.35 V     65 W

Brisbane Athlon 64 X2 5000+               1 MB       1.25 - 1.35 V     65 W

Windsor Athlon 64 X2 5000+ EE             1 MB       1.20 - 1.25 V     65 W

Windsor Athlon 64 X2 5000+                1 MB       1.30 - 1.35 V     89 W

Windsor Athlon 64 X2 5200+ EE             2 MB       1.20 - 1.25 V     65 W

Windsor Athlon 64 X2 5200+                2 MB       1.30 - 1.35 V     89 W

Windsor Athlon 64 X2 5400+                1 MB       1.30 - 1.35 V     89 W

Windsor Athlon 64 X2 5600+                2 MB       1.30 - 1.35 V     89 W

Windsor Athlon 64 X2 6000+                2 MB       1.35 - 1.40 V     125 W
   Random access memory (usually known by its acronym,
    RAM) is a type of data storage used in computers. It takes
    the form of integrated circuits that allow the stored data to
    be accessed in any order — that is, at random and without
    the physical movement of the storage medium or a
    physical reading head.
   The word "random" refers to the fact that any piece of data
    can be returned in a constant time, regardless of its
    physical location and whether or not it is related to the
    previous piece of data. This contrasts with storage
    mechanisms such as tapes, magnetic discs and optical
    discs, which rely on the physical movement of the
    recording medium or a reading head. In these devices, the
    movement takes longer than the data transfer, and the
    retrieval time varies depending on the physical location of
    the next item.


    RAM – Random Access Memory
   System RAM speed is controlled by bus width and bus speed.
    Bus width refers to the number of bits that can be sent to the
    CPU simultaneously, and bus speed refers to the number of times
    a group of bits can be sent each second. A bus cycle occurs
    every time data travels from memory to the CPU. For example, a
    100-MHz 32-bit bus is theoretically capable of sending 4 bytes
    (32 bits divided by 8 = 4 bytes) of data to the CPU 100 million
    times per second, while a 66-MHz 16-bit bus can send 2 bytes of
    data 66 million times per second. If you do the math, you'll find
    that simply changing the bus width from 16 bits to 32 bits and
    the speed from 66 MHz to 100 MHz in our example allows for
    three times as much data (400 million bytes versus 132 million
    bytes) to pass through to the CPU every second.




RAM
Connects to:
PCB or motherboard via one of
     oSocket
     oIntegration
Types:

SDRAM - synchronous dynamic random access memory
DDR - double-data-rate synchronous dynamic random access memory
RDRAM - Direct Rambus DRAM or DRDRAM
DDR 2
DDR 3
Common Manufacturers:
Micron Technology
Samsung
Kingston Technology
Corsair Memory
Mushkin
  The "memory wall" is the growing disparity between CPU and
  memory speeds. From 1986 to 2000, CPU speed improved at
  an annual rate of 55% while memory speed only improved at
  10%. Given these trends, it was expected that memory latency
  would become an overwhelming bottleneck in computer
  performance.
  Currently, CPU speed improvements have slowed significantly
  partly due to major physical barriers and partly because current
  CPU designs have already hit the memory wall in some sense.




Memory Wall
 RAM Capacities usually doubles for
  example: 128, 256, 512, 1024
 If a motherboard has 3 RAM slots what
  combo will give you a gig of RAM?




RAM Memory
Hard Drives
Hard Drives
Hard Drives
Hard Drives
   Nearly every desktop computer and
    server in use today contains one or more
    hard-disk drives. Every mainframe and
    supercomputer is normally connected to
    hundreds of them. You can even find VCR-
    type devices and camcorders that use
    hard disks instead of tape. These billions
    of hard disks do one thing well -- they
    store changing digital information in a
    relatively permanent form. They give
    computers the ability to remember things
    when the power goes out.
   Hard disks were invented in the 1950s.
    They started as large disks up to 20
    inches in diameter holding just a few
    megabytes. They were originally called
    "fixed disks" or "Winchesters" (a code
    name used for a popular IBM product).
    They later became known as "hard disks"
    to distinguish them from "floppy disks."
    Hard disks have a hard platter that holds
    the magnetic medium, as opposed to the
    flexible plastic film found in tapes and
    floppies.
   At the simplest level, a hard disk is not
    that different from a cassette tape. Both
    hard disks and cassette tapes use the
    same magnetic recording techniques.
    Hard disks and cassette tapes also share
    the major benefits of magnetic storage --
    the magnetic medium can be easily
    erased and rewritten, and it will
    "remember" the magnetic flux patterns
    stored onto the medium for many years.
   A typical desktop machine will have a hard disk with a capacity of
    between 60 and 500 gigabytes. Data is stored onto the disk in the
    form of files. A file is simply a named collection of bytes. The bytes
    might be the ASCII codes for the characters of a text file, or they
    could be the instructions of a software application for the computer to
    execute, or they could be the records of a data base, or they could be
    the pixel colors for a GIF image. No matter what it contains, however,
    a file is simply a string of bytes. When a program running on the
    computer requests a file, the hard disk retrieves its bytes and sends
    them to the CPU one at a time.
   There are two ways to measure the performance of a hard disk:
     ◦ Data rate - The data rate is the number of bytes per second that
       the drive can deliver to the CPU. Rates between 5 and 40
       megabytes per second are common.
     ◦ Seek time - The seek time is the amount of time between when
       the CPU requests a file and when the first byte of the file is sent to
       the CPU. Times between 10 and 20 milliseconds are common.
   The other important parameter is the capacity of the drive, which is
    the number of bytes it can hold.
 A video card, (also referred to as a graphics accelerator card, display
 adapter, graphics card, and numerous other terms), is an item of
 personal computer hardware whose function is to generate and output
 images to a display.
 The term is usually used to refer to a separate, dedicated expansion
 card that is plugged into a slot on the computer's motherboard, as
 opposed to a graphics controller integrated into the motherboard chipset.
 Some video cards offer added functionalities, such as video capture, TV
 tuner adapter, MPEG-2 and MPEG-4 decoding or even FireWire, mouse,
 light pen, joystick connectors, or even the ability to connect two
 monitors.




Video Cards
Video Cards
   The images you see on your monitor are made of tiny dots
    called pixels. At most common resolution settings, a screen
    displays over a million pixels, and the computer has to
    decide what to do with every one in order to create an
    image. To do this, it needs a translator -- something to
    take binary data from the CPU and turn it into a picture
    you can see. Unless a computer has graphics capability
    built into the motherboard, that translation takes place on
    the graphics card.




Video Cards
   A graphics card's job is complex, but its
    principles and components are easy to
    understand. In this article, we will look at
    the basic parts of a video card and what
    they do. We'll also examine the factors
    that work together to make a fast,
    efficient graphics card.




Video Cards
   The graphics card creates a wire frame image, then
    fills it in and adds textures and shading.
Video Cards
   The CPU, working in conjunction with
    software applications, sends information
    about the image to the graphics card. The
    graphics card decides how to use the
    pixels on the screen to create the image.
    It then sends that information to the
    monitor through a cable.




Video Card Basic
   Creating an image out of binary data is a
    demanding process. To make a 3-D image, the
    graphics card first creates a wire frame out of
    straight lines. Then, it rasterizes the image (fills
    in the remaining pixels). It also adds lighting,
    texture and color. For fast-paced games, the
    computer has to go through this process about
    sixty times per second. Without a graphics card
    to perform the necessary calculations, the
    workload would be too much for the computer to
    handle.



Video Cards
Video Cards
Video Cards
Video Cards
   A top-of-the-line graphics card is easy to spot. It has lots
    of memory and a fast processor. Often, it's also more
    visually appealing than anything else that's intended to go
    inside a computer's case. Lots of high-performance video
    cards are illustrated or have decorative fans or heat sinks.
   But a high-end card provides more power than most
    people really need. People who use their computers
    primarily for e-mail, word processing or Web surfing can
    find all the necessary graphics support on a motherboard
    with integrated graphics. A mid-range card is sufficient for
    most casual gamers. People who need the power of a high-
    end card include gaming enthusiasts and people who do
    lots of 3-D graphic work.




Choosing a Graphics Card
    Some cards, like the ATI All-in-Wonder, include
connections for televisions and video as well as a TV tuner.
   A good overall measurement of a card's performance is its frame
    rate, measured in frames per second (FPS). The frame rate
    describes how many complete images the card can display per
    second. The human eye can process about 25 frames every
    second, but fast-action games require a frame rate of at least 60
    FPS to provide smooth animation and scrolling. Components of
    the frame rate are:
    ◦ Triangles or vertices per second: 3-D images are made of triangles, or
      polygons. This measurement describes how quickly the GPU can calculate the
      whole polygon or the vertices that define it. In general, it describes how quickly
      the card builds a wire frame image.
    ◦ Pixel fill rate: This measurement describes how many pixels the GPU can
      process in a second, which translates to how quickly it can rasterize the image.




Choosing a Video Card
   The graphics card's hardware directly affects its speed. These are
    the hardware specifications that most affect the card's speed and
    the units in which they are measured: GPU clock speed (MHz)
    ◦   Size of the memory bus (bits)
    ◦   Amount of available memory (MB)
    ◦   Memory clock rate (MHz)
    ◦   Memory bandwidth (GB/s)
    ◦   RAMDAC speed (MHz)
   The computer's CPU and motherboard also play a part, since a
    very fast graphics card can't compensate for a motherboard's
    inability to deliver data quickly. Similarly, the card's connection to
    the motherboard and the speed at which it can get instructions
    from the CPU affect its performance.




Choosing a Video Card
   Some people choose to improve their
    graphics card's performance by manually
    setting their clock speed to a higher rate,
    known as overclockings. People usually
    overclock their memory, since
    overclocking the GPU can lead to
    overheating. While overclocking can lead
    to better performance, it also voids the
    manufacturer's warranty.

Overclocking
   Common Manufacturers
    ◦   Creative Labs
    ◦   Realtek
    ◦   C-Media
    ◦   M-Audio




Audio Cards
   Before the invention of the sound card, a PC could make one
    sound - a beep. Although the computer could change the beep's
    frequency and duration, it couldn't change the volume or create
    other sounds. At first, the beep acted primarily as a signal or a
    warning. Later, developers created music for the earliest PC
    games using beeps of different pitches and lengths.



Audio Cards
 ◦ In addition to the basic components needed for sound
   processing, many sound cards include additional hardware or
   input/output connections, including:
 ◦ Digital Signal Processor (DSP): Like a graphics processing unit
   (GPU), a DSP is a specialized microprocessor. It takes some of
   the workload off of the computer's CPU by performing
   calculations for analog and digital conversion. DSPs can
   process multiple sounds, or channels, simultaneously. Sound
   cards that do not have their own DSP use the CPU for
   processing.




Audio Cards
 ◦ Memory: As with a graphics card, a sound card can use its own
   memory to provide faster data processing.
 ◦ Input and Output Connections: Most sound cards have, at the very
   minimum, connections for a microphone and speakers. Some include
   so many input and output connections that they have a breakout box,
   which often mounts in one of the drive bays, to house them. These
   connections include:
     Multiple speaker connections for 3-D and surround sound
     Sony/Philips Digital Interface (S/PDIF), a file transfer protocol for
      audio data. It uses either coaxial or optical connections for input to
      and output from the sound card.
     Musical Instrument Digital Interface (MIDI), used to connect
      synthesizers or other electronic instruments to their computers.
     FireWire and USB connections, which connect digital audio or video
      recorders to the sound card




Audio Cards
Audio Cards
Audio Cards
Audio Cards
Audio Cards
Audio Cards
Audio Cards
Audio Cards
 A network card, network adapter or
  NIC (network interface card) is a piece of
  computer hardware designed to allow
  computers to communicate over a
  computer network.
 MAC Address – media access control




NIC Cards
   Although other network technologies exist, Ethernet
    has achieved near-ubiquity since the mid-1990s.
    Every Ethernet network card has a unique 48-bit
    serial number called a MAC address, which is stored
    in ROM carried on the card. Every computer on an
    Ethernet network must have a card with a unique
    MAC address. No two cards ever manufactured share
    the same address. This is accomplished by the
    Institute of Electrical and Electronics Engineers
    (IEEE), which is responsible for assigning unique MAC
    addresses to the vendors of network interface
    controllers.




MAC Address
   Speeds:                   Common
    ◦   10 Mbit/s              Manufacturers:
    ◦   100 Mbit/s             ◦   Belkin
    ◦   1000 Mbit/s            ◦   Intel
    ◦   up to 160 Gbit/s       ◦   Realtek
                               ◦   Linksys




NIC Cards
   Speeds:                   Common
    ◦   10 Mbit/s              Manufacturers:
    ◦   100 Mbit/s             ◦   Belkin
    ◦   1000 Mbit/s            ◦   Intel
    ◦   up to 160 Gbit/s       ◦   Realtek
                               ◦   Linksys




NIC Cards
   The word "modem" is a contraction of
    the words modulator-demodulator. A
    modem is typically used to send digital
    data over a phone line. The sending
    modem modulates the data into a
    signal that is compatible with the phone
    line, and the receiving modem
    demodulates the signal back into
    digital data. Wireless modems convert
    digital data into radio signals and back.



Modems
 Modems came into existence in the 1960s as a way to allow
 terminals to connect to computers over the phone lines.
 A typical arrangement is shown below:




Modems
   When personal computers started
    appearing in the late 1970s, bulletin
    board systems (BBS) became the rage.
    A person would set up a computer with a
    modem or two and some BBS software,
    and other people would dial in to connect
    to the bulletin board. The users would run
    terminal emulators on their computers
    to emulate a dumb terminal.




Modems
   People got along at 300 bps for quite a
    while. The reason this speed was tolerable
    was because 300 bps represents about 30
    characters per second, which is a lot more
    characters per second than a person can
    type or read. Once people started
    transferring large programs and images to
    and from bulletin board systems, however,
    300 bps became intolerable.



Modems
   Modem speeds went through a series of steps at
    approximately two-year intervals:
   300 bps - 1960s through 1983 or so
   1200 bps - Gained popularity in 1984 and 1985
   2400 bps
   9600 bps - First appeared in late 1990 and early
    1991
   19.2 kilobits per second (Kbps)
   28.8 Kbps
   33.6 Kbps
   56 Kbps - Became the standard in 1998
   ADSL, with theoretical maximum of up to 8
    megabits per second (Mbps) - Gained popularity
    in 1999




Modems
WiFi
 A wireless network uses radio waves, just like cell
  phones, televisions and radios do. In fact,
  communication across a wireless network is a lot like
  two-way radio communication. Here's what happens:
 A computer's wireless adapter translates data
  into a radio signal and transmits it using an
  antenna.
 A wireless router receives the signal and
  decodes it. It sends the information to the
  Internet using a physical, wired Ethernet
  connection.
 The process also works in reverse, with the
  router receiving information from the Internet,
  translating it into a radio signal and sending it
  to the computer's wireless adapter.




WiFi – Wireless Fidelity
   The radios used for WiFi communication
    are very similar to the radios used for
    walkie-talkies, cell phones and other
    devices. They can transmit and receive
    radio waves, and they can convert 1s and
    0s into radio waves and convert the radio
    waves back into 1s and 0s.




WiFi – Wireless Fidelity
   WiFi radios have a few notable differences from other
    radios:
     ◦ They transmit at frequencies of 2.4 GHz or 5GHz. This
       frequency is considerably higher than the frequencies
       used for cell phones, walkie-talkies and televisions. The
       higher frequency allows the signal to carry more data.




WiFi – Wireless Fidelity
   They use 802.11 networking standards, which come
    in several flavors:
    ◦ 802.11b was the first version to reach the marketplace. It's
      the slowest and least expensive standard, and it's becoming
      less common as faster standards become less expensive.
      802.11b transmits in the 2.4 GHz frequency band of the
      radio spectrum. It can handle up to 11 megabits of data per
      second, and it uses complimentary code keying (CCK)
      coding.
    ◦ 802.11g also transmits at 2.4 GHz, but it's a lot faster than
      802.11b -- it can handle up to 54 megabits of data per
      second. 802.11g is faster because it uses orthogonal
      frequency-division multiplexing (OFDM), a more efficient
      coding technique.
    ◦ 802.11a transmits at 5GHz and can move up to 54 megabits
      of data per second. It also and uses OFDM coding. Newer
      standards, like 802.11n, can be even faster than 802.11g.
      However, the 802.11n standard isn't yet final.




WiFi – Wireless Fidelity
   If you want to take advantage of public WiFi
    hotspots or start a wireless network in your
    home, the first thing you'll need to do is make
    sure your computer has the right wireless gear.
    Most new laptops and many new desktop
    computers come with built-in wireless
    transmitters. If your laptop doesn't, you can
    buy a wireless adapter that plugs into the PC
    card slot or USB port. Desktop computers can
    use USB adapters, or you can buy an adapter
    that plugs into the PCI slot inside the
    computer's case. Many of these adapters can
    use more than one 802.11 standard.




WiFi – Wireless Fidelity
   If you want to take advantage of public WiFi hotspots
    or start a wireless network in your home, the first
    thing you'll need to do is make sure your computer
    has the right wireless gear. Most new laptops and
    many new desktop computers come with built-in
    wireless transmitters. If your laptop doesn't, you can
    buy a wireless adapter that plugs into the PC card
    slot or USB port. Desktop computers can use USB
    adapters, or you can buy an adapter that plugs into
    the PCI slot inside the computer's case. Many of
    these adapters can use more than one 802.11
    standard.




WiFi – Wireless Fidelity
   If there is any one component that is
    absolutely vital to the operation of a
    computer, it is the power supply. Without
    it, a computer is just an inert box full of
    plastic and metal. The power supply
    converts the alternating current (AC) line
    from your home to the direct current (DC)
    needed by the personal computer. In this
    article, we'll learn how PC power supplies
    work and what the wattage ratings mean.


Power Supplies
 Power supplies, often referred to as
  "switching power supplies", use switcher
  technology to convert the AC input to
  lower DC voltages.
 The typical voltages supplied are:
    ◦ 3.3 volts
    ◦ 5 volts
    ◦ 12 volts




Power Supplies
   The 3.3- and 5-volts are typically used by digital
    circuits, while the 12-volt is used to run motors
    in disk drives and fans. The main specification of
    a power supply is in watts. A watt is the product
    of the voltage in volts and the current in
    amperes or amps. If you have been around PCs
    for many years, you probably remember that the
    original PCs had large red toggle switches that
    had a good bit of heft to them. When you turned
    the PC on or off, you knew you were doing it.
    These switches actually controlled the flow of
    120 volt power to the power supply.


Power Supplies
   A 400-watt switching power supply will
    not necessarily use more power than a
    250-watt supply. A larger supply may be
    needed if you use every available slot on
    the motherboard or every available drive
    bay in the personal computer case. It is
    not a good idea to have a 250-watt supply
    if you have 250 watts total in devices,
    since the supply should not be loaded to
    100 percent of its capacity.


Power Supply Wattage
             PC Item                      Watts

Accelerated Graphics Port (AGP) card    20 to 30W


Peripheral Component Interconnect
                                           5W
            (PCI) card


  small computer system interface
                                        20 to 25W
          (SCSI) PCI card

          floppy disk drive                5W

       network interface card              4W

         50X CD-ROM drive               10 to 25W
                RAM                    10W per 128M


     5200 RPM Integrated Drive
                                         5 to 11W
  Electronics (IDE) hard disk drive


   7200 RPM IDE hard disk drive          5 to 15W

Motherboard (without CPU or RAM)        20 to 30W

       550 MHz Pentium III                 30W

       733 MHz Pentium III                23.5W

         300 MHz Celeron                   18W
          600 MHz Athlon                   45W
 The PC power supply is probably the most failure-prone item in a
  personal computer. It heats and cools each time it is used and
  receives the first in-rush of AC current when the PC is switched
  on. Typically, a stalled cooling fan is a predictor of a power supply
  failure due to subsequent overheated components. All devices in
  a PC receive their DC power via the power supply. A typical failure
  of a PC power supply is often noticed as a burning smell just
  before the computer shuts down. Another problem could be the
  failure of the vital cooling fan, which allows components in the
  power supply to overheat. Failure symptoms include random
  rebooting or failure in Windows for no apparent reason.
 For any problems you suspect to be the fault of the power supply,
  use the documentation that came with your computer. If you
  have ever removed the case from your personal computer to add
  an adapter card or memory, you can change a power supply.
  Make sure you remove the power cord first, since voltages are
  present even though your computer is off.

Power Supply Problems

								
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