Transcript ch4Colon - La Salle University

The Components of the System Unit
Chapter 4
By: Janice Colon
The System Unit
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The system unit is a box-like case that stores the electronic
components of the computer used to process information.
Electronics components and other storage devices are located
inside the system unit.
Components inside the system unit include:
 Processor
 Memory
 Module
 Cards
 Ports
 Connectors
The Motherboard
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The motherboard or the system board, is the
main circuit board in the system unit.
 Mother board includes different types of
chips.
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A chip is a small piece of semi conducting material, on
which integrated circuits are etched.
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There are various chip packages such as;
 Dual inline package
 Pin grid array package
 Flip chip package
 Single edge contact cartridge
Central Processing Unit
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The central processing unit, or the
processor, interprets and carries out the basic
instructions that operate a computer.
Control Unit/
Arithmetic/
Logic Unit
Input Devices
Memory
Storage Devices
Output Devices
Central Processing Unit
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The CPU contains the control unit and the
arithmetic/logic unit.
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The control unit directs and coordinates most of the
operations in the computer.
For every instruction, the control unit repeats a set of four
basic operations called machine cycle:
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Fetch - obtain program instruction or data item from
memory
Decode - translate instruction into commands
Execute - carry out command
Store - write result to memory
The arithmetic/logic unit performs arithmetic, comparison,
and logical operations.
Central Processing Unit
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Pipelining
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Registers
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With pipelining the CPU begins executing a second instruction
before it completes the first instruction.
The registers temporarily hold data and instructions.
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Stores location from where instruction was fetched
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Stores instruction while it is being decoded
o
Stores data while ALU processes it
The system Clock
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The system clock control the timing of all computer operations.
The clock speed is the speed at which a processor executes
instructions.
Central Processing Unit
Comparison of Personal Computer Processors
The most popular personal computer processor are:
Pentium
Xeon
Athlon
Celeron
Itanium
Duron
Processor Installation and Upgrades
Instead of buying a new computer it might be better to upgrade
your processor to increase the computer’s performance.
Processor upgrades are identified as:
A chip for chip upgrade
A piggyback upgrade
A daughterboard upgrade
Data Representation
Most computers are digital which
means they only recognize only two
discrete states: on and off.
1
ON
0
OFF
Data Representation
Computers uses a binary system to recognize the two
states.
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The binary system is a number that has just two unique
digits, 0, 1, called bits.
Bit is the smallest unit of data the computer can represent.
When eight bits are grouped together as a unit, they form a
byte, which provides enough different combinations of 0’s
and 1’s to represent 256 individual characters.
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These characters include numbers, uppercase and lowercase
letters of the alphabet, and punctuation marks.
Combinations of 0’s and 1’s are defined by patterns called
coding scheme.
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Two popular coding schemes are:
 The American Standard Code for Information Exchange
 The Extended Binary Coded Decimal Interchange Code
Memory
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What is memory?
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Temporary storage area for data, instructions, and
information.
It consists on one or more chips on motherboard
How is memory measured?
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By the number of bytes available
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Kilobyte (KB)
Megabyte (MB)
Gigabyte (GB)
Memory
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There are two types of system unit memory.
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Volatile memory, which loses its contents when the computers
power is turned off.
Nonvolatile memory, which does not loses its content when the
computers power is turned off.
Memory in a computer refers to RAM (random access
memory)
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Consists of memory chips that can be read and written to by
the processor and other devices.
Also called main memory or primary storage.
Most RAM is volatile.
The more RAM a computer has the faster it responds.
Memory
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How Application Programs Transfer In and Out of
RAM?
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Step 1. When the computer is running, certain operating
system files are in RAM. The operating system displays on the
screen.
Step 2. When you start a program, the program loads into RAM
from the hard disk. As you are creating the document the
information is on RAM and it shows in the screen.
Step 3. When you quit the program, RAM may be used to store
another program or data. The original program is removed
from the screen, and the operating system’s user interface re
appears.
Step 4. When you quit a program, its program instructions are
removed from RAM. The Web browser no longer is displayed on the
screen.
Memory
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What are two basic types of RAM chips?
Static RAM
(SRAM)
Dynamic RAM
(DRAM)
Used for special
application such
as cache
Most Common
Type
Faster and
more reliable
than DRAM
chips
Faster variations
of DRAM are SDRAM
and RDRAM
Memory
ROM (read-only memory) refers to memory
chips that only can be read and used, which
means they cannot be modified.
 ROM is nonvolatile memory (NVM), meaning
that its contents are not lost when the
computer’s power is turned off.
 A variation of the ROM chip, called
programmable read-only memory (PROM),
is a blank chip on which you can place
items permanently.
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Memory
 Flash
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Memory
also known as flash ROM or flash RAM, is
nonvolatile memory that can be erased
electronically and reprogrammed.
 CMOS
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Another type of memory chip, it stores
configuration information about the computer and
uses battery power to retain information when the
power to the computer is turned off.
Expansion Slots and
expansion cards
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An expansion slot is an opening, or socket, where you can insert
a circuit board into the motherboard.
 These circuit boards are called; card, expansion board,
expansion board, adapter card, adapter, interface card, addin, and add-on.
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There are four types of expansion cards found in most of
today’s computers;
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Video card
Sound card
Network interface card
Modem card
Ports
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A cable often attaches external devices to the
system unit. A port is the point of attachment
to the system unit.
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Ports have different types of connectors which are
used to connect a cable with a device.
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Male connectors have one or more exposed pins.
Female connectors have matching holes to accept the
pins.
Ports
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Most computers have three types of ports;
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Serial port
Parallel port
Universal serial bus
Buses
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How buses contribute to a computers processing
speed?
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Bits are transfer internally within the circuitry of the computer
along electrical channels.
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These channels are called a bus. They allow the various
devices inside and attached to the system unit to communicate
with each other.
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The bus width determines the number of bits that can be
transferred at one time.
In most computer word size is the number of bits the processor
can interpret and execute at a given time.
A computer has two basic types of buses
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System bus – connects the CPU to main memory.
Expansion bus – allows the CPU to communicate with peripheral
devices.
Bay
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A bay is an open area inside the system unit
in which you can install additional equipment.
 Drive bays
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External drive bay – allows access from outside
the system unit.
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Floppy A disk
DVD
Zip drives
Internal drive bay – concealed entirely within the
system unit.
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Hard disk drive
Power Supply
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Power supply is the component in the system
unit that converts the wall outlet AC power
into DC power.
 AC adapter – an external power supply.
Mobile Computers
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What is a mobile computer?
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Looks like a notebook
Weights between 2.5 and 8 pounds
Mobile computers system unit contain;
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Motherboard
Processor
Keyboard
Speakers
Display