system unit.ppt

The Components of the system unit

System Unit is a case that contains
electronic components of the computer
used to process data.
 Made of metal or plastic to protects the
internal components from damage.
 All computers have a system unit. It is
available in variety of shapes & sizes.

Handheld controller
System unit
System
unit
System
unit
System
unit
System unit

 Processor interprets & carries out the basic
instructions that operate a computer.
 Memory holds data waiting to be processed
& instruction waiting to be executed.
 Processor & Memory are connected to a
circuit board called the motherboard.
 Adapter cards are circuit boards that
provide connections and functions not built
into the motherboard.
 Devices outside the system unit often attach
to the ports.
 A drive bay holds one or more disk drive.
 The Power supply provide the computer

Motherboard , called system board.
It is a main circuit board of the system unit.
Many electronic components attach to the
motherboard, others are built into it. Ex:
adapter cards, a processor chip and a
memory module.

Processor, called the central processing unit (CPU),
Microprocessor.
Its contain a control unit & an arithmetic
logic unit (ALU).
These 2 components work together to
perform processing operations.

MEMORY
INPUT
DEVICES
OUTPUT
DEVICES
Processor
Control
Unit
ALU
Processor
Control
Unit
ALU
Instructions
Data
Information
Instructions
Data
Information
Data
Storage
Devices
information

The operations typically performed by a CPU
are:
1. CPUs control the reading of programs and input
files.
1. Its activates input unit to read program and data.
2. Controls the transmission of program & data files
from disk to main memory.
2. CPUs process data according to instructions in a
program.
1. Data can be processed arithmetically- number
can be added, subtracted, multiplied and divided.
2. Logical tests can be performed on data. E.g.,
comparison.

The Arithmetic Logic Unit performs arithmetic,
comparison and other operations.
The Control Unit
 Handles the transmission of data into and
out of the CPU and supervises its overall
operations.
 Its interprets each instruction issued by a
program & then initiates the appropriate
action to carry out the instruction.

Components of the system unit…Processor
Machine Cycle
For every instruction, a processor repeats a set of four
basic operations:
1. Fetching process of obtaining a program
instruction or data item from memory.
2. Decoding process of translating the
instruction into signals the computer can
execute.
3. Executing process of carrying out the
commands.
4. Storing, if necessary. Means writing the

Processor
What is pipelining?
 CPU begins fetching second instruction before
completing machine cycle for first instruction
 Results in faster processing

Registers
The CPU contain special storage areas called
registers.
Their function is to hold instructions, data values,
memory addresses of both the instructions and
data.
There are 4 basic types of it:
1. Instruction register hold instruction
2. Address register hold address of( data , next
instruction ).
3. Storage register store data retrieved from main
memory prior to processing.

The System Clock
 Every CPU has a clock, It’s a small quartz
crystal circuit , which generates regular
clock pulses that control the timing of all
computer operations.
 Processing actions occur at each “tick” of
the electronic clock.
 The Speed of the clock determines the
speed at which the CPU can process data.

Clock Speed
 Speed is measured in megahertz (MHz) or
(GHz).
 1MHz is a million pulses per second.
 1GHz is a billion pulses per second.
 The faster the clock speed, the more
instruction the processor can execute per
second (hertz).
 Clock speed measure the internal speed.

Processor
• Processor What are heat sinks, heat pipes, and
liquid cooling?
• Heat sink—component with fins that cools
processor
• Heat pipe—smaller device for notebook
computers
• Liquid cooling—uses a continuous flow of fluids
to transfer heat away

Processor
• Processor What is parallel processing?
• Using multiple processors simultaneously to
execute a program faster
• Requires special software to divide problem and
bring results together

Comparison of Personal computer
Processors
The leading processor chip manufacturers for
personal computers are
 Intel
 AMD ( advanced Micro Devices)
 Transmeta
 IBM
 Motorola

Processors
Intel
Pentium M processor used in Notebook &
Tablet Computers .
 Xeon & Itanium processor, are ideal for
workstations and servers.

Processors
AMD is the leading manufacturer of Intel-
compatible processors.
It less expensive than Intel processors.
Transmeta is manufacturer of Intel-compatible
processors, specializes in processors for
mobile computers and devices.

Processors
IBM processor or Motorola processor had a
different design from the Intel-style
processor.
Until recently, Apple computers used only an
IBM processor or Motorola processor.
Today’s Apple use Intel processors.

How the CPU represents data
 Binary system based on two digits 0 and 1.
0 : off
1 : on
 Bit is a the smallest unit of data the
computer can process.
 Byte a group of 8 bits.
 A byte can be represent characters.
 Characters can be a letter, digit, or symbol.

How the CPU represents data
The different combinations of 0s and 1s are
defined by patterns called a coding
schema.
There are tow popular coding scheme:
1. ASCII stands for American Standard Code for
Information Interchange.
2. EBCDIC stand for Extended Binary Coded
Decimal Interchange Code.

Memory
 Memory consist of electronic
components that store instructions
waiting to be executed by the
processor, data needed by those
instructions, and the results of
processed data ( information).
 Memory usually consist of one or more
chips on the motherboard or some
other circuit board in the computer.

Memory
Stores 3 basic categories of items:
1. The operating system and other system
software that control or maintain the
compute and its devices
2. Application programs
3. The data being processed by the
application programs and resulting
information.

Memory sizes
It’s the number of bytes the chip or devices has
available for storage.
Term Abb.
Approximate no. of
byte
Exact no. of
byte
Kilobyte KB or K 1000 1,024
Megabyte MB 1Million 1,048,576
Gigabyte GB 1Billion 1,073,741, 824
Terabyte TB 1 Trillion 1,099,511,627,776

Type of Memory
The system unit contains tow types of memory:
1. Volatile memory -
 Loses its contents .
 Temporary memory.
 Example, RAM.
2. Nonvolatile memory-
 doesn't lose its content when power is
removed form the computer.
 Permanent memory.
 Example, ROM, Flash memory, and CMOS.

RAM ( Random Access Memory ), Also Called
main memory.
 consists of memory chips that can be read
from and written to by the processor and other
devices.
 The content my changed.
Saving is a process of copying items from
RAM to a storage device such as a hard disk.

RAM ( Random Access Memory )
Three basic types of RAM chips exist:
 DEAM Dynamic RAM
 Chips must be re-energized constantly or they
lost their contents.
 SRAM Static RAM
 Faster and more reliable than any variation of
DRAM chips.
 They don’t have to be re-energized as often as
DRAM chips.
 MRAM Magnetoresistive RAM
 Stores data using magnetic charges instead of
electrical charges.

RAM ( Random Access Memory )
RAM chips usually reside on a memory
module, which is a small circuit board.
Memory slots on the motherboard hold
memory modules.

RAM configurations
 The amount of RAM necessary in a
computer often depends on the types of
software you plan to use.
 The more RAM a computer has, the faster
the computer will respond.
 The amount of RAM in computers
purchased today ranges from 256 MB to 16
GB.

Cache Memory Helps speed the processes of the
computer because it stores
frequently used instruction and data.
There are 2 types of cache:
1. L1 cache
 Is built directly in the processor chip.
 It has small capacity ranging from 8KB to 128KB.
2. L2 cache
 Slower than L1, has a Larger capacity ranging
from 64KB to 16 MB.
 Advanced transfer cache, a type of L2 built
directly on the processor chip.

Cache Memory
 Cache speeds up processing time because it
store frequently used instructions and data.
 When the processor needs an instruction or
data, it searches memory in this order : L1 >
L2 > RAM > hard disk or CD.

ROM ( Read Only Memory)
 The data on most ROM chips cannot be
modified.
 Main function of ROM chips often record
data, instructions, or information on the chip
which is important to boot(start) the system.
This is the bootstrap process.
 Computers almost always contain a small
amount of read-only memory that holds

 PROM (programmable read-only memory): A
PROM is a memory chip on which you can store a
program. But once the PROM has been used, you
cannot wipe it clean and use it to store something
else. Like ROMs, PROMs are non-volatile.
 EPROM (erasable programmable read-only
memory): An EPROM is a special type of PROM
that can be erased by exposing it to ultraviolet light.
 EEPROM (electrically erasable programmable
read-only memory): An EEPROM is a special type
of PROM that can be erased by exposing it to an

Flash Memory A special type of EEPROM
Is a type of nonvolatile memory that can be
erased electronically and rewritten.
 Most computers use flash memory to hold
their startup instructions because it allows
the computer easily to update its contents.
 Many modern PCs have their BIOS stored
on a flash memory chip so that it can easily
be updated if necessary. Such a BIOS is
sometimes called a flash BIOS.

CMOS ( Complementary metal-oxide semiconductor.)
 Some RAM chips, flash memory chip and other
types of memory chips use CMOS because it
provides high speeds & consumes little power.
 CMOS technology uses battery power to retain
information even when the power to the computer is
off.
 Personal computers also contain a small amount of
battery-powered CMOS memory to hold the date,
time, and system setup parameters.

Memory Access Time
 It is the amount of time takes the processor
to read data, instructions, information from
memory.
 It’s affects how fast the computer process
data.
 Access time on memory can be more than
200,000 times faster than accessing data on
a hard disk because the mechanical motion

Memory Access Time
Term Abb. Speed
Millisecond ms One-thousandth of a second
Microsecond μs One-millionth of a second
Nanosecond ns One-billion of a second
Picosecond ps One-trillionth of a second

Expansion Slot and Adapter Cards
 Expansion slot is a socket on the motherboard
that can hold an adapter card
 Adapter card sometimes called an expansion card
 is a circuit board that enhances functions of a
component of the system unit and/or provides
connections to peripherals.
 Peripheral is a device that connects to a system
unit and is controlled by the processor. Ex:
keyboard, printer.

Types of adapter cards
Adapter Card Purpose
Graphics
accelerator
Increases the speed at which graphics are displayed
Modem Connect other computers through telephone or cable TV
line
Network Connects other computers and peripherals
Sound Connects speakers or microphone
Video Connects a monitor

Expansion Slot and Adapter Cards
 Sometimes all functionality is built into the adapter
card.
 With others, a cable connects the Adapter card to
device.
 Some motherboard include all necessary
capabilities and do not require adapter cards.
 Other motherboard may require adapter cards to
provide capabilities such as sound card & video
card.

Ports and Connectors
Port is the point at which a peripheral attaches
to or communicates with a system unit so
the peripheral can send data to or receive
information from the computer.
 the term jack sometimes is used to identify
audio and video ports.
 Port have a different types of connectors, A
connectors joins a cable to a peripheral.

Serial Ports is a type of interface that connects
a device to the system unit by transmitting
data one bit at a time.
 Its for device that no need fast data
transmission rate such as mouse, Keyboard
or modem.
 COM Port ( communications port) on system
unit is one type of serial port.

Parallel Ports is an interface that connects a
device by transferring more than one bit at a
time.
 Can transfer eight bits of data ( one byte)
simultaneously through eight separate lines
in a single cable.
 The printers using a parallel port.

USB Ports, Short for universal serial bus port.
 Can connect up to 127 different peripherals
together with a single connector.
 The latest version of USB called USB 2.0.
 USB 2.0 is a more advanced and faster
USB, with speeds 40 times higher than that
of its predecessor.
 USB hub is a device that plugs in a USB
port on the system & contains multiple USB
ports.

FireWire Ports Previously called an IEEE 1394
port.
 It is similar to a USB port in that it can
connect multiple type of device that require
faster data transmission speeds to a single
connector, such as digital video camera,
color printers, scanners, .. etc.
 Allow you to connect up to 63 devices
together.
 You can use a FireWire hub to attach
multiple devices to a single FireWire port.

Special-Purpose Ports
These ports are not included in typical
computers.
 MIDI Port
 SCSI Port
 IrDA Port
 Bluetooth Port

MIDI Port, short for musical instrument digital
interface.
 Serial port
 Connect the system unit to keyboard.
SCSI Port
 A special high-speed parallel port.
 Allow you to attach SCSI peripherals such
as disk driver and printers.

IrDA refers to Infrared Data Association
 A standard for communication between
devices (such as computers, PDAs and
mobile phones) over short distances using
infrared signals.
 For these wireless devices to transmit
signals to a computer, both the computer
and the device must have an IrDA port.
 To ensure nothing obstructs the path of the
infrared light wave, you must align the IrDA
port on the device with the IrDA port on the

Bluetooth Port ,An alternative to IrDA.
 It is s technology uses radio waves to
transmit data between two devices.
 Unlike IrDA, do not have to be aligned with
each other.
 If your computer not Bluetooth –enable you
can use Bluetooth wireless port adapter or
Bluetooth PC Cards.

BUSES
a set of electronic signal pathways that allows
information and signals to travel between
components inside or outside of a computer.
Buses transfer bits
 from input devices to memory.
 from the processor to memory, and from memory to
the processor.
 from memory to output devices.

BUSES
A computer's bus can be divided into two different types,
Internal and External.
 The Internal Bus is part of the motherboard and
connects the processor to main memory. It's also
referred to as the System Bus.
 The External Bus allows the processor to
communicate with peripherals. It is generally
slower than the system bus. Another name for
the External Bus, is the Expansion Bus.
Buses consist of two part: Data bus and Address bus.

BUSES
 Data bus transfers actual data.
 Address bus transfers information about data
location on memory.
 The size of a bus, called the bus width, determines
the number of bits the computer can transmit at one
time.
 Bus Width is indicating how fast data is transmitted
within the CPU.
 Every bus also has a clock speed.

Power Supply
Is a component of the system unit that supply
computer with power.

Question Time

- Memory stores 3 basic categories of items ….&…..&…..
- …Helps speed the processes of the computer because
it stores frequently used instruction and data.
- …. is a circuit board that enhances functions of
component of the system unit and/or provides
connections to peripherals.
-…..is the point at which a peripheral attaches to or
communicates with a system unit so the peripheral can
send data to or receive information from the computer.
- ……… is an interface that connects a device by
transferring more than one bit at a time.
- Buses consist of two part: ……… and ……...

system unit.ppt

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