Technology in Action
© 2008 Prentice-Hall, Inc.
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Technology in Action
Chapter 9
Behind the Scenes:
A Closer Look at System Hardware
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Chapter Topics
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•
•
•
•
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Computer switches
Binary number system
Inside the CPU
Cache memory
Types of RAM
Computer buses
Creating faster CPUs
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Binary Language
• Computers work in binary
language
• Consists of two numbers: 0 and 1
• Everything a computer does is broken
down into a series of 0s and 1s
• Switches: Devices inside the
computer that can be flipped between
these two states: 1 or 0, on or off
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Switches
• Nonmechanical devices in
computers that open and close
circuits
• Types of electrical switches:
Vacuum Tube
– Vacuum tubes
– Transistors:
• Semiconductors
– Integrated circuits
Transistors
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Integrated Circuits
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Switches Representing Data
• The on/off state of a switch represents one
bit of data
OFF
ON
• Bit (binary digit)
– On = 1
– Off = 0
0
1
OR
1
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= 1 bit
0
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The Binary Number System
• Describes a number as powers of 2
• Also referred to as base 2 numbering
system
• Used to represent every piece of data
stored in a computer: all of the numbers,
letters, and instructions
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The Binary Number System
• Number systems are organized ways to represent
numbers
• Each number in one system has a corresponding
number in another.
Binary
Base
10
128
2x64
64
2x32
32
2x16
16
2x8
8
2x4
4
2x2
2
2x1
1
0
1
0
1
1
0
0
1
0+
0+
0 + 64 + 0 +
16 + 8 +
1 = 89
01011001
=
89
Binary
Base 10
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Representing Letters and Symbols
• American Standard
Code for Information
Interchange (ASCII)
• Unicode
– 8 bits = 1 byte = alphanumeric
character or symbol
– 256 different combinations
– 16 bits equal 1 byte
– 65,000 different
combinations, used for all
languages
01100001 = a
ASCII
01000001 = A
00100011 = #
01101101 = m
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The CPU:
Processing Digital Information
• The CPU is the brains of
the computer
• Different types of CPUs
– Intel and AMD chips: Used in
most Windows-based PCs
– Apple systems use different
CPU design
• Differentiating CPUs
– Processing power
– Clock speed and cache
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Processors on the Market Today
Processor
Manufacturer
Number of
Transistors
Typical
Clock Speed
Levels of
Cache Storage
Description
Athlon 64 FX –
60
AMD
233 million
2.6 GHz
2
64-bit processor for heavy
computation and demanding video
gaming needs.
Core Duo
Intel
151.6 million
1.6 - 2.16 GHz
2
Designed specifically for mobile
computers; transfers power only to
those areas of the processor that
need it, improving battery life.
Itanium 2
Intel
410 million
1.3 – 1.66 GHz
3
Seen in high-end server computers.
Pentium 4
Extreme
Edition 955
Intel
225 million
3.46 GHz
Each processor
core has its own 2
MB L2Cache
This processor uses a dual–core
design and hyperthreading to
Process four tasks at once.
Pentium D Dual
Core
Intel
230 million
2.8 - 3.4 GHz
2
New dual-core processor for more
efficient multitasking. No
hyperthreading capabilities.
PowerPC G4
Freescale
Semiconductor
(once part of
Motorola)
57 million
1.5 – 1.67 GHz
3
Until 2006, powered the Apple line
of computers.
Dual Core
PowerPC G5
IBM
58 million
2.0 - 2.5 GHz
2
Powerful 64-bit processor for heavy
computational needs.
Sempron
AMD
68.5 million
2.0 GHz
2
Affordable performance for today’s
value-conscious buyers of desktop
PCs.
Turion
AMD
114 million
1.6 – 2.4 GHz
2
Optimized for better performance in
thinner and lighter laptops for
longer battery life and compatible
with wireless technologies.
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The CPU Machine Cycle
• Fetch
– The program’s binary code is “fetched” from its
temporary location in RAM and moved to the CPU
• Decode
– The program’s binary code is decoded into commands
that the CPU understands.
• Execute
– The ALU performs the calculations.
• Store
“Inside the Chip” by
Intel
Video Clip
– The results are stored in the registers
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The System Clock
• Located on the motherboard
• Controls the CPU’s processing cycles
• Clock cycle
– Pulse or tick
• Clock speed
– Number of pulses per second
– Measured in hertz (Hz)
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The Control Unit
• Manages the switches inside the CPU
• Is programmed by CPU designers to
remember the sequence of processing
stages for that CPU
• Moves each switch to its correct setting
(on or off)
• Then performs the work of that stage
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The Arithmetic Logic Unit (ALU)
• Part of the CPU designed to perform
mathematical operations (addition, subtraction,
multiplication, division, etc.)
• Also performs logical OR, AND, and NOT
operations
• Is fed data from the CPU registers
– Word size: Number of bits a computer can work with
at a time
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Cache Memory
• Small amount of
memory located on the
CPU chip or near it
• Stores recent or
frequently used
instructions and data
• Used for quick access
by the CPU
• Different levels of cache
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Cache Memory
• Different levels of cache
– Level 1 Cache
• A block of memory that is
built onto the CPU chip for
the storage of data or
commands that have just
been used.
• Level 2 cache is located on
the CPU chip but is slightly
farther away from the CPU,
or it’s on a separate chip
next to the CPU
• Some newer CPUs have
an additional third level of
cache memory storage
called Level 3 cache.
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RAM: The Next Level of
Temporary Storage
• Volatile: When you turn off your computer,
the data stored in RAM is erased
• Several kinds of RAM exist
• Each type of RAM has a different design
– Some types work at much faster speeds
– Some transfer data more quickly
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Types of RAM: DRAM
• Dynamic RAM (DRAM)
–
–
–
–
Cheapest and most basic type of RAM
Loses its electrical charge
Needs to be refreshed
Many types of DRAM
• SDRAM: Synchronous DRAM
– Faster than traditional DRAM
• DDR SDRAM: Double the data rate SDRAM
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Types of RAM: SRAM
• Static RAM (SRAM)
– Does not lose its electrical charge
– Faster than DRAM
– More expensive than DRAM
– Used only in locations like cache
memory where the system demands the
fastest possible storage
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Buses: The CPU’s Data Highway
• Bus
– Electrical pathway used to move data between
components
– Local bus: Connects the CPU with the memory
– Expansion bus: Connects the CPU with peripheral
devices
01100010
01001000
01110011
00100111
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Bus Performance
• Bus clock speed
– Rate of speed data moves
from one location to another
– Measured in MHz (millions
of clock cycles per second)
• Bus width
– The number of bits of data
moved on a bus at any one
time
– Measured in bits
• 16 bits
• 32 bits
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Types of Expansion Buses
• ISA and EISA
– Found on older computers
– Connects mouse, modem, and sound card
• PCI
– Faster than ISA and EISA
– Found on modern computers
– Connects network, modem, and sound cards
• AGP
– Used for three-dimensional graphics
– Connects the graphics card and memory
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Moore’s Law
• Number of transistors on a CPU will
double every 18 months
• First chip had 29,000 transistors
• Pentium chip 169,000,000 transistors
• Moore’s Law has been accurate for more
than 40 years
• Law has remained accurate into the 21st
century
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Making Computers Faster
• As an instruction is processed, the CPU
runs through the four stages of processing
in a sequential order:
– Fetch
– Decode
– Execute
– Store.
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Making Computers Faster
• Pipelining
– A technique that allows the CPU to work on
more than one instruction (or stage of
processing) at a time, thereby boosting CPU
performance.
– Used in some fashion in all modern CPUs.
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Making Computers Faster
Pipelining
• Instead of the CPU carrying out one step
of the machine cycle on every pulse of the
system clock, the CPU performs different
parts of the cycle simultaneously,
theoretically making the CPU four times
faster.
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Making Computers Faster
Pipelining
• Chip makers have also designed special
instruction sets to handle multimedia
content, again speeding up the overall
performance of the system.
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Making Computers Faster
• Pipelining: The CPU processes more than
one instruction at a time
Nonpipelined CPU
Instruction 1
Fetch
Decode
Execute
Store
Instruction 2
Fetch
Decode
Execute
Store
Pipelined CPU
Instruction 1
Fetch
Decode
Instruction 2
Fetch
Decode
Store
Execute
Store
Fetch
Decode
Execute
Store
Instruction 4
Fetch
Decode
Execute
Instruction 3
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Execute
Store
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Making Computers Faster
• Dual processing
– Two CPUs on the same
system
– Each processor shares
the workload
Dual processors
• Parallel processing
– Network of computers
– Each computer works on
a portion of the problem
simultaneously
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Dual-core Processing and
Hyperthreading
• Two separate parallel processing paths
• Almost as fast as two separate processors
• Hyperthreading allows the processor to
run four tasks at once
• Allows multiple applications to execute
much more quickly
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Computing Clusters
• Group of computers
– Allows computers to share computational
tasks
• Connected by “clustering software”
• Load-balancing principle
– Allows a busy computer in the cluster to pass
off the instruction to a computer with unused
resources
• Not as fast as supercomputers
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Computing Clusters
• Can be set up on Linux systems for free
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Chapter 9 Summary Questions
• What is a switch and how does it work in a
computer?
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Chapter 9 Summary Questions
• What is the binary number system and
what role does it play in computer system?
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Chapter 9 Summary Questions
• What is inside the CPU and how do these
components operate?
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Chapter 9 Summary Questions
• How does a CPU process data and
instructions?
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Chapter 9 Summary Questions
• What is cache memory?
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Chapter 9 Summary Questions
• What types of RAM are there?
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Chapter 9 Summary Questions
• What is a bus and how does it function in
a computer system?
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Chapter 9 Summary Questions
• How do manufacturers make CPUs so that
they run faster?
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