Chapter 4
The Components of
the System Unit
Chapter 4 Objectives
Differentiate
Differentiateamong
amongvarious
variousstyles
styles
ofofsystem
systemunits
units
Identify
Identifychips,
chips,adapter
adaptercards,
cards,and
andother
other
components
componentsofofaamotherboard
motherboard
Describe
Describethe
thecomponents
componentsofofaaprocessor
processorand
andhow
how
they
theycomplete
completeaamachine
machinecycle
cycle
Identify
Identifycharacteristics
characteristicsofofvarious
variouspersonal
personal
computer
computerprocessors
processorson
onthe
themarket
markettoday
today
Define
Defineaabit
bitand
anddescribe
describehow
howaaseries
seriesofofbits
bits
represents
representsdata
data
Explain
Explainhow
howprograms
programstransfer
transferinin
and
andout
outofofmemory
memory
Differentiate
Differentiateamong
amongthe
thevarious
various
types
typesofofmemory
memory
Describe
Describethe
thetypes
typesof
ofexpansion
expansionslots
slotsand
and
adapter
adaptercards
cards
Explain
Explainthe
thedifference
differenceamong
amongaaserial
serialport,
port,aa
parallel
parallelport,
port,aaUSB
USBport,
port,and
andother
otherports
ports
Describe
Describehow
howbuses
busescontribute
contributeto
toaa
computer’s
computer’sprocessing
processingspeed
speed
Identify
Identifycomponents
componentsininmobile
mobilecomputers
computers
and
andmobile
mobiledevices
devices
Next
1
The System Unit
What is the system unit?
Ø
Case that contains electronic
components of the computer used
to process data
§
Sometimes called
the chassis
p. 180 Fig. 4-1
Next
The System Unit
What are common components inside the system unit?
Ø
Ø
Ø
Processor
Memory
Adapter cards
§
§
§
§
Ø
Ø
Ø
Sound card
Modem card
Video card
Network card
power supply
drive bays
processor
memory
ports
sound card
Ports
Drive bays
Power supply
network card
p. 181 Fig. 4-2
modem card
video card
Next
2
The System Unit
What is the motherboard?
Ø
Ø
Ø
adapter cards
processor chip
Main circuit
board in system
unit
Contains adapter
cards, processor
chips, and
memory chips
Also called
system board
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Clock Motherboards
below Chapter 4
p. 182 Fig. 4-3
memory chips
memory slots
Expansion
slots for
adapter cards
motherboard
Next
The System Unit
What is a chip?
Ø
Ø
Small piece of semi-conducting
material on which integrated
circuits are etched
§ Integrated circuits contain
many microscopic pathways
capable of carrying electrical
current
Chips are packaged so they can
be attached to a circuit board
dual inline
packages (DIP)
holds memory
chips
pin grid
array (PGA)
package
holds processor
chips
Click to view animation
p. 182 Fig. 4-4
Next
3
Processor
What is the central processing unit (CPU)?
Ø Interprets
and carries
out basic instructions
that operate a computer
Processor
Control
Control
Unit
Unit
§ Control unit directs and
coordinates operations in
computer
§ Arithmetic logic unit
Input
(ALU) performs
Devices
arithmetic, comparison,
and logical operations
Ø Also
called the processor
Arithmetic
Arithmetic
Logic
Logic Unit
Unit (ALU)
(ALU)
Instructions
Data
Information
Data
Memory
Output
Devices
Information
Instructions
Data
Information
Storage
Devices
p. 183 Fig. 4-5
Next
Processor
What is a machine cycle?
Ø
Four operations of the CPU comprise a machine cycle
Step 1. Fetch
Obtain program instruction
or data item from memory
Memory
Step 2.
Decode
Step 4. Store
Translate
instruction into
commands
Write result to memory
Processor
ALU
Step 3. Execute
Control Unit
Carry out command
p. 184 Fig. 4-6
Next
4
Processor
What is pipelining?
Ø
Ø
CPU begins fetching second instruction before
completing machine cycle for first instruction
Results in faster processing
p. 185 Fig. 4-7
Next
Processor
What is a register?
Ø
Temporary high-speed storage area that holds
data and instructions
Stores location
from where instruction
was fetched
Stores
instruction while it is
being decoded
Stores data
while ALU
computes it
Stores results
of calculation
p. 185
Next
5
Processor
What is the system clock?
Ø
Ø
Controls timing of all computer operations
Generates regular electronic pulses, or ticks, that set
operating pace of components of system unit
Pace of system
clock is clock speed
Most clock speeds are
in the gigahertz (GHz)
range (1 GHz = one
billion ticks of system
clock per second)
Each tick
is a
clock cycle
Processor speed can
also be measured in
millions of instructions
per second (MIPS)
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Clock Speed
below Chapter 4
p. 185
Next
Processor
How do personal computer processors compare?
Comparison of Widely Used
Personal Computer Processors
Name
Click to view video
Clock
Speed
Itanium 2
Xeon
2002
2001
1.3–1.5 GHZ
1.4–3.06 GHZ
Itanium
Pentium
Pentium
Pentium
Celeron
Operon
Athlon
Athlon
2001
2000
1999
1999
1998
2003
2002
2001
733–800 MHZ
1.4–3.2 GHZ
500–900 MHZ
400 MHZ –1.4 GHZ
266 MHZ –2.6 GHZ
2–2.4 GHZ
1.53–2.25 GHZ
1.33–2.26 GHZ
1999
500 MHZ –1.4 GHZ
Athlon
p. 186 Fig. 4-8
Date
Introduced
4
III Xeon ™
III
MP
XP
Next
6
Processor
Which processor should you select?
Ø The faster the processor, the more expensive the computer
Intel Processor
Itanium or Xeon
Pentium family
Desired Clock Speed
1.3 GHz and up
3.0 GHz and up
2.4 GHz to 3.0 GHz
Up to 2.4 GHz
Celeron
2.2 GHz and up
Click to view video
p. 188 Fig. 4-9
Next
Processor
What are the types of processor upgrades?
ChipChip-for chip upgrade
replace the chip
Piggyback upgrade
stack new chip on top of old one
Daughterboard upgrade
chip is on adapter card that plugs into motherboard
p. 188
Next
7
Processor
What is a zero-insertion force (ZIF) socket?
Ø
Allows you to install and remove chips with no force
lever
lever
Step 1.
Step 2.
Step 3.
Lift the lever on the socket.
Insert the chip.
Push the lever down.
p. 189 Fig. 4-10
Next
Processor
What are heat sinks and heat pipes?
Ø
Ø
Heat sink— component
with fins that cools
processor
Heat pipe — smaller
device for notebook
computers
heat sink fan
e
heat sink
p. 190 Fig. 4-11
Next
8
Processor
What is a coprocessor?
Chip
Chip that
that assists
assists processor
processor in
in
performing
performing specific
specific tasks
tasks
One
-point coprocessor,
floating
coprocessor
One type
type isis aa floatingfloating-point
coprocessor, also
also
known
known as
as aa math
math or
or numeric
numeric coprocessor
coprocessor
p. 190
Next
Processor
What is parallel processing?
Ø
Ø
Using multiple
processors
simultaneously to
execute a
program faster
Requires special
software to divide
problem and
bring results
together
p. 190 Fig. 4-12
Control Processor
Processor 1
Processor 2
Processor 3
Processor 4
Memory
Memory
Memory
Memory
Results combined
Next
9
Data Representation
How do computers represent data?
Ø
Most computers are digital
§ Recognize only two
discrete states: on or off
§ Use a binary system to
recognize two states
§ Use Number system with
two unique digits: 0 and
1, called bits (short for
binary digits)
p. 191 Fig. 4-13
Next
Data Representation
What is a byte?
Ø
Ø
Eight bits grouped together as a unit
Provides enough different combinations of 0s and 1s
to represent 256 individual characters
§
§
§
p. 191 Fig. 4-14
Numbers
Uppercase
and lowercase
letters
Punctuation
marks
Next
10
Data Representation
What are three popular coding systems to represent data?
Ø
Ø
Ø
ASCII— American Standard Code for Information Interchange
EBCDIC— Extended Binary Coded Decimal Interchange Code
Unicode— coding scheme capable of representing all
world’s languages
ASCII
Symbol
EBCDIC
00110000
00110001
00110010
00110011
0
1
2
3
11110000
11110001
11110010
11110011
p. 192 Fig. 4-15
Next
Data Representation
How is a letter converted to binary form and back?
Step 1.
Step 2.
The user presses
the capital letter D
(shift+D key) on
the keyboard.
Step 4.
After processing, the binary
code for the capital letter D is
converted to an image, and
displayed on the output device.
p. 193 Fig. 4-16
An electronic signal for the
capital letter D is sent to the
system unit.
Step 3.
The signal for the capital letter D
is converted to its ASCII binary
code (01000100) and is stored in
memory for processing.
Next
11
Memory
Seat #2B4
What is memory?
Ø
Ø
Ø
Seat #2B3
Electronic components that
store instructions, data, and
results
Consists of one or
more chips on
motherboard or
other circuit board
Each byte stored
in unique location
called an address,
similar to seats
on a passenger train
p. 193 Fig. 4-17
Next
Memory
How is memory measured?
Ø
By number of bytes available for storage
p. 194 Fig. 4-18
Term
Abbreviation
Kilobyte
Megabyte
Gigabyte
Terabyte
KB or K
MB
GB
TB
Approximate Size
1 thousand bytes
1 million bytes
1 billion bytes
1 trillion bytes
Next
12
Memory
What is random access memory (RAM)?
Memory chips that can be
read from and written
to by processor
Also called
main memory
or primary
storage
Most RAM is
volatile , it is lost
volatile,
when computer’
computer’s
power is
turned off
The more RAM a
computer has, the
faster it responds
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
RAM
below Chapter 4
p. 195
Next
Memory
How do program instructions transfer in and out of RAM?
RAM
Operating system
instructions
Operating system
interface
Step 1. When you start the computer, certain
operating system files are loaded into RAM from
the hard disk. The operating system displays the
user interface on the screen.
Step 2. When you start a Web browser, the
Web browser
instructions
Web browser
window
program’s instructions are loaded into RAM from
the hard disk. The Web browser window is
displayed on the screen.
Step 3. When you start a word processing
Word processing
program instructions
Word processing
program window
program, the program’s instructions are loaded
into RAM from the hard disk. The word
processing program, along with the Web Browser
and certain operating system instructions are in
RAM. The word processing program window is
displayed on the screen.
RAM
Step 4. When you quit a program, such as the
Web browser, its program instructions are
removed from RAM. The Web browser no longer
is displayed on the screen.
p. 195 Fig. 4-19
Web browser program
instructions are
removed from RAM
Web browser
window no longer is
displayed on desktop
Next
13
Memory
What are two basic types of RAM chips?
Static
RAM
(SRAM)
Most
common
type
Faster
variations
of DRAM are
SDRAM and
RDRAM
Dynamic
RAM
(DRAM)
Used for
special
applications
such as
cache
Faster and
more reliable
than DRAM
chips
Future: Magnetoresistive RAM (MRAM)
p. 196
Next
Memory
dual inline memory module
Where does memory reside?
Ø
Ø
Resides on small circuit
board called memory
module
Memory slots on
motherboard hold memory
modules
p. 196 Fig. 4-20
memory chip
memory slot
Next
14
Memory
How much RAM does an application require?
Ø
Software package
System Requirements
typically indicates
Windows XP Home Edition/Professional
• Intel Pentium processor at 233MHZ or higher
RAM requirements
• AMD K6 (Athlon Duron Family processor at 233MHZ or higher
• 64 MB of RAM
For optimal
performance, you
need more than
minimum specifications
®
Ø
p. 197 Fig. 4-21
Next
Memory
How much RAM do you need?
Ø
Depends on type of applications you intend to run
on your computer
RAM
Use
p. 197 Fig. 4-22
128 to 256 MB
• Home and business
users managing
personal finance
• Using standard
application software
such as word processing
• Using educational
or entertainment
CD-ROMs
• Communicating with
others on the Web
256 to 1 GB
• Users requiring more advanced
multimedia capabilities
• Running number-intensive
accounting, financial, or
spreadsheet programs
• Using voice recognition
• Working with videos, music, and
digital imaging
• Creating Web sites
• Participating in video conferences
• Playing Internet games
1 GB and up
• Power users creating
professional Web sites
• Running sophisticated
CAD, 3D design, or
other graphics-intensive
software
Next
15
Memory
What is cache?
Ø
Ø
Helps speed computer processes by storing frequently used
instructions and data
Also called memory cache
§
§
§
§
L1 cache built into processor
L2 cache slower but has larger capacity
L2 advanced transfer cache is faster,
built directly on processor chip
L3 cache is separate from processor
chip on motherboard (L3 is only
on computers that use L2 advanced
transfer cache)
Click to view Web Link,
click Chapter 4, Click
Web Link from left
navigation, then click
Cache below Chapter 4
p. 198 Fig. 4-23
Next
Memory
What is read-only memory (ROM)?
Memory chips that store
permanent data
and instructions
Nonvolatile memory,
memory , it is not
lost when computer’
computer’s
power is turned off
Three types:
EEPROM
(e lectrically
e rasable programmable
read
ead--only memory)
emory)—
—
Type of PROM
containing microcode
PROM
programmer
(programmable
can erase
read
ead--only
memory)
emory)—
—
Blank ROM
chip onto which
a programmer
can write permanently
Firmware —
Manufactured with
permanently written
data, instructions,
or information
p. 198
Next
16
Memory
What is flash memory?
Ø
Ø
Nonvolatile memory that can be erased electronically and
reprogrammed
Used with PDAs, digital cameras, digital cellular phones, music players,
digital voice recorders, printers, Internet receivers, and pagers
Step 3.
Step 1.
Purchase and download MP3 music tracks
from a Web site. With one end of a special
cable connected to the system unit, connect
the other end into the MP3 player.
Flash memory chip
To headphones
Plug the headphones into the MP3
player, push a button on the MP3
player, and listen to the music
through the headphones.
From computer
Flash memory card
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Flash Memory
below Chapter 4
p. 199 Fig. 4-24
Step 2.
Instruct the computer to copy the MP3 music track
to the flash memory chip in the MP3 player.
MP3 Player
Next
Memory
What is CMOS?
Complementary
metal-oxide
semiconductor
memory
Uses battery
power to retain
information when
other power is
turned off
p. 200
Used in some
RAM chips, flash
memory chips, and
other types of
memory chips
Stores date,
time, and
computer’s
startup
information
Next
17
Memory
What is access time?
Ø
Ø
Ø
Amount of time it takes processor
to read data from memory
Measured in nanoseconds (ns),
one billionth of a second
It takes 1/10 of a second to blink
your eye; a computer can perform
up to 10 million operations in same amount of
time
Term
Millisecond
Microsecond
Nanosecond
Picosecond
Speed
One-thousandth of a second
One-millionth of a second
One-billionth of a second
One-trillionth of a second
p. 200 Figs. 4-25-4-26
Next
Expansion Slots and Adapter Cards
Types of Adapter Cards
What is an adapter card?
Ø
Ø
Enhances system unit or
provides connections to
external devices called
peripherals
Also called an expansion card
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Adapter Cards
below Chapter 4
p. 201 Fig. 4-27
Next
18
Expansion Slots and Adapter Cards
What is an expansion slot?
Ø
Ø
An opening, or socket,
on the motherboard
that can hold an
adapter card
With Plug and Play,
the computer
automatically
configures cards
and other devices
as you install them
p. 201 Fig. 4-28
Next
Expansion Slots and Adapter Cards
What are PC cards and flash memory cards?
Ø
Ø
A PC card adds memory, storage,
sound, fax/modem,
communications, and other
capabilities to notebook computers
A flash memory card allows users
to transfer data from mobile
devices to desktop computers
§
Hot plugging allows you to insert
and remove cards while computer
is running
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
PC Cards
below Chapter 4
p. 202 Fig. 4-29–4-30
Next
19
Ports and Connectors
What are ports and connectors?
Ø
Ø
Port connects external devices to system unit
Connector joins cable to peripheral
§
Available in one of two genders: male and female
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Ports and Connectors
below Chapter 4
p. 203 Fig. 4-31–4.32
Next
Ports and Connectors
What are different types of connectors?
p. 204 Fig. 4-33
Next
20
Ports and Connectors
What is a serial port?
Ø
Ø
Transmits one bit of data at a
time
Connects slow-speed devices,
such as mouse, keyboard,
modem
p. 205 Fig. 4-34
Next
Ports and Connectors
What is a parallel port?
Ø
Connects devices that can
transfer more than one bit at
a time, such as a printer
p. 205 Fig. 4-35
Next
21
Ports and Connectors
What are USB ports?
USB (universal serial bus) port can connect
up to 127 different peripherals together
with a single connector type
PCs
PCs typically
typically have
have
four
four to
to eight
eight USB
USB ports
ports
on
on front
front or
or back
back of
of
the
the system
system unit
unit
Single
Single USB
USB port
port can
can
be
be used
used to
to attach
attach
multiple
multiple peripherals
peripherals
in
in aa daisy
daisy chain
chain
First
First USB
USB
device
device connects
connects
to
to USB
USB port
port
on
on computer
computer
p. 206
Third
Third USB
USB
device
device connects
connects
to
to second
second USB
USB
device,
device, and
and so
so on
on
Second
Second USB
USB
device
device connects
connects
to
to first
first USB
USB
device
device
Next
Ports and Connectors
What are special-purpose ports?
Ø
Allow users to attach specialized peripherals (digital video
cameras, color printers, scanners, and disk drives) or
transmit data to wireless devices
§
§
§
§
§
p. 206 Fig. 4-36
FireWire port
MIDI (Musical
Instrument Digital
Interface) port
SCSI (small
computer system
interface) port
IrDA (Infrared Data
Association) port
Bluetooth port
Next
22
Buses
What is a bus?
Ø
Channel that allows devices
inside computer to
communicate with each other
§
§
§
System bus connects processor
and RAM
Bus width determines number
of bits transmitted at one time
Word size is the number of
bits processor can interpret
and execute at a given time
Click to view Web Link,
click Chapter 4, Click Web Link
from left navigation, then click
Buses
below Chapter 4
p. 208 Fig. 4-38
Next
Buses
What is an expansion bus?
Ø
Allows processor to communicate with peripherals
p. 209 Fig. 4-39
Next
23
Bays
What is a bay?
Ø
Ø
Open area inside
system unit used to
install additional
equipment
Drive bays typically
hold disk drives
p. 210 Fig. 4-40
Next
Power Supply
What is a power supply?
Converts
AC Power
into
DC Power
Fan keeps
system unit
components
cool
External peripherals
might use an AC
adapter, which is an
external power supply
p. 211
Next
24
Mobile Computers and Devices
What is a mobile computer?
Ø
Notebook, weighing between 2.5 and 8 pounds, or
mobile device such as a PDA
flash memory card
PDA
PC Cards in
PC Card slots
CD or DVD drive
disk in floppy
disk drive or
Zip ® disk drive
p. 211 Fig. 4-41
battery
notebook computer
Next
Mobile Computers and Devices
What is in the system unit of a mobile computer?
Ø
Motherboard,
processor, and
memory— also
devices such as the
keyboard, speakers,
and display
p. 212 Fig. 4-42
Next
25
Mobile Computers and Devices
What ports are on a notebook computer?
p. 212 Fig. 4-43
Next
Mobile Computers and Devices
What ports are on a tablet PC?
p. 212 Fig. 4-44
Next
26
Putting It All Together
What are suggested processor, clock speed, and RAM
requirements based on the needs of various types of users?
p. 213 Fig. 4-45
Next
Summary of the Components of the System Unit
Components
Componentsof
ofthe
thesystem
systemunit
unit
How
Howmemory
memorystores
storesdata,
data,instructions,
instructions,
and
andinformation
information
Sequence
Sequenceof
ofoperations
operationsthat
thatoccur
occurwhen
whenaa
computer
computerexecutes
executesan
aninstruction
instruction
Comparison
Comparisonof
ofvarious
variouspersonal
personalcomputer
computer
processors
processorson
onthe
themarket
markettoday
today
Chapter 4 Complete
27