Computer Hardware

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Computer Hardware

• Part 2

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Microprocessors

• popular microprocessors
• Intel
• AMD (Advanced Micro Devices)
• Motorola
• AMD and Intel are comparable
• Pentium 4
• Itanium
• Celeron
• Athlon
• Duron
• The microprocessor thats best for you depends
  upon your budget and the type of work and play
  you plan to do

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Random Access Memory

• RAM (random access memory) - an area of the
  computer that temporarily holds data before and
  after it is processed
• as you type, characters are held in RAM
• It holds the data and the instructions for
  processing the data
• It even houses OS instructions

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Random Access Memory

• RAM is primary storage (main memory)
• Measured in megabytes (MB)
• Todays computers have between 64 and 512
  megabytes of RAM
• Amount of RAM depends on software you use
• You can purchase additional RAM
• A computer can use disk storage to simulate RAM.
  This is called virtual memory
• Not as fast as RAM

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• RAM components vary in speed, technology, and
  configuration
• Speed is measured in nanoseconds. 1 nanosecond is
  1 billionth of a second
• It can also be expressed in MHz (millions of
  cycles per second)
• Most computers use SDRAM (synchronous dynamic
  RAM)
• Another type is RDRAM (Rambus dynamic RAM)

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RAM Disk Storage

• Capacitors are microscopic electronic parts that
  hold the electronic signals for the code that
  represents data.
• charged capacitor ON
• discharged capacitor OFF
• each bank of capacitors holds eight bits
• Disk storage is fairly permanent
• Floppy disks, hard disks, or CDs

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Read-Only Memory

• ROM (read-only memory) is one or more chips
  containing instructions that help a computer
  prepare to process tasks
• ROM is permanent and non-volatile
• Only way to change the instructions on a ROM chip
  is to replace the chip

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Read-Only Memory

• Since RAM is empty when a computer is turned on,
  ROM BIOS is used
• ROM BIOS (basic input/output system) is a set of
  instructions that tells computer how to access
  the disk drives and peripheral devices
• Once operating system is loaded, the computer can
  understand your input, run software and access
  your data

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CMOS memory

• A computer needs a semi-permanent way of keeping
  boot data, such as the number of hard disk
  sectors and cylinders
• CMOS memory - holds data but requires very little
  power to retain its contents
• Retains important computer settings after you
  turn the power off
• can run by a battery on the motherboard
• housed within the same chip carrier as ROM BIOS
• Some computers have plug and play feature for
  updating CMOS

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Storage Devices

• A storage device, such as a floppy disk drive, a
  hard drive, zip drive, and a CD-ROM drive, is
  used to store the data
• A storage medium is the disk, tape, CD, DVD,
  paper or other substance that contains data
• Storing Data
• Retrieving Data

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Storage Technologies

• Magnetic storage
• It stores data by magnetizing microscopic
  particles on the disk or tape surface
• Read-write head - mechanism in the disk drive
  that reads and writes magnetized particles that
  represent data
• Data stored on magnetic media such as floppy
  disks can be altered by dust, smoke, heat, and
  mechanical problems.
• Some experts estimate that the reliable life span
  of data stored on magnetic media is about three
  years

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Storage Technologies

• Optical storage
• It stores data as microscopic light spots (lands)
  and dark spots (pits) on the disk surface
• Data stored on an optical storage device is less
  susceptible to environmental damage

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Which storage technology is best?

• Versatility
• can access data from different media
• Durability
• less susceptible to damage
• Storage capacity - maximum amount of data that
  can be stored on a storage medium

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Which storage technology is best?

• Speed - measured by access time and data transfer
  rate
• Access time - average time it takes a computer to
  locate data and read it
• millisecond one-thousandth of a second
• Random access - ability of a device to jump
  directly to the track or sector holding the data
• floppy disk, hard drive, CD, DVD, zip disks

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Floppy disk Technology

• A floppy disk is a round piece of flexible mylar
  plastic covered with a thin layer of magnetic
  oxide and sealed inside a protective casing
• 3 ½ diskettes have capacity of 1.44 MB
• Other floppy disk types
• ZIP disks 100 MB and 250 MB
• Superdisks 120 MB
• Disk density - closeness and size of magnetic
  particles it stores
• Zip disks and Superdisks store data at a higher
  density than a standard 3 ½ floppy disk
• Major advantage portability
• Major disadvantage not a particularly speedy
  device and limited storage capacity

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Hard Disk Technology

• It provides lots of storage capacity
• It provides faster access to files than floppy
  disk drives
• It is economical
• Hard disk platter - a flat, rigid disk made of
  aluminum or glass and coated with magnetic oxide
• density far exceeds floppy disk
• Hard disk - one or more platters and their
  associated read-write heads.
• preferred type of main storage
• A hard drive mechanism includes a circuit board
  called a controller that positions the disk and
  read-write heads to locate data

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Hard Disk Technology

• Removable hard disk - hard disks that can be
  inserted and removed from drive
• increase storage capacity
• provides security for data
• RAID - (redundant array of independent disks)
• type of hard disk storage
• found on mainframe and microcomputer
  installations
• contains many disk platters
• provides redundancy
• faster data access

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Tape Storage

• Tape
• most popular form of storage in 1960s
• Recent revival in tape storage for backing up
  data, not for principal storage device.
• Tape backup - copy of data on hard disk stored on
  magnetic tape.
• Requires sequential access
• Inconvenient and slow
• Data is arranged as essentially a long sequence
  of bits that begin at one end of the tape and
  stretches to the other
• Tape drives are available in either internal or
  external models

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CD Technology

• CD-ROM
• stands for Compact Disc Read-Only Memory
• data stamped on when manufactured
• coated with clear plastic, durable
• estimated life exceeds 500 years
• inexpensive to manufacture
• ideal for distribution of large files
• A single CD-ROM holds up to 650 MB
• It is very durable
• Original CD-ROM had speeds of 150 KB per second
• Today, speeds of 24x or higher (24 x 150 KB per
  second)

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DVD Technology

• DVD (digital video disc or digital versatile
  disc)
• variation of CD technology
• designed to provide enough storage capacity for a
  full length movie
• will replace video tape (experts believe)
• DVD-ROM disk (sometimes used for DVD-Video)
• stamped with data when manufactured
• cannot change or add data
• stores 4.7 GB
• ideal for games, maps, large databases

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Input/Output Devices

• Data Bus carries data from one component to
  another
• I/O (computer jargon for input/output) refers to
  collecting data and transporting results.
• Expansion bus - the segment of the data bus that
  transports data between RAM and peripheral devices

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Input/Output Devices

• Peripheral Devices
• Display devices
• Printers