Title: Chapter 4 Computer Hardware
1Chapter 4Computer Hardware
- Information Technology in Theory
- By Pelin Aksoy and Laura DeNardis
2Objectives
- Identify some important historical milestones in
the development of computers - Understand logic gates and how computers use them
to process information - Identify the fundamental components of a computer
- Understand how computer performance depends on
factors such as processor speed, chip set, bus
width, bus speed, number of CPUs, and instruction
set
3Objectives (continued)
- Examine future trends in computing and societal
issues related to these advances - Understand the physical principles of data
storage and the difference between mechanical,
magnetic, optical, and electronic storage
4A Brief History of Computers
- Computing devices trace back at least to the
Abacus - Mechanical calculation tools in the 1600s
included William Oughtreds slide rule,
BlaisePascals arithmetic machine, and Leibnizs
step reckoner - Calculation tools of the 1800s included Charles
Babbages Difference and Analytical engines - Augusta Ada Byron, the Countess of Lovelace,
worked with Babbage in programming the analytical
engine - Herman Hollerith developed the tabulating machine
to tabulate the 1890 US census data using punch
cards
5A Brief History of Computers (continued)
- The punch card concept is attributed to Joseph
Marie Jacquard - The 1940s spurred big advancements in computing
- John Vincent Atanasoff and Clifford Berry at the
Iowa State College built the ABC - Konrad Zuse built the Z3
- Howard Aiken built the Mark I, which was
programmed by Grace Murray Hopper - British scientists built the Colossus
- John Mauchly and J. Presper Eckert built the
ENIAC
6A Brief History of Computers (continued)
- The transistor and integrated circuit enable
smaller computers compared to vacuum tubes - Popular Electronics ran a feature story about a
home do-it-yourself computer kit called the
Altair - Radio Shack began to sell the TRS-80 home
computer, and Apple Computer Inc. introduced its
own line of home computers - These advances, and the introduction of IBMs
personal computer (PC) in 1981, contributed to
the explosion of computers in all facets of
modern life
7A Brief History of Computers (continued)
- A variety of social and economic factors, along
with advances in microprocessors and distributed
networks, led to the introduction of mobile,
wireless, and handheld computers
8Digital Logic
- A computer has one or more main chips called the
microprocessor, which performs most of the
processing, and several other supporting chips - Integrated circuits such as microprocessors are
built by combining transistors together to create
logic gates - These basic building blocks can be combined to
create successively larger building blocks, which
may subsequently be combined to create complex
circuitry and packaged with other components
within a carrier to create integrated circuits
such as microprocessors
9Digital Logic (continued)
10Digital Logic (continued)
- Integrated circuits are built using the following
types of logic gates - The difference between these logic gates is
essentially the way the transistors within them
are connected to each other - NOT gate (inverter)
- AND gate
- NAND (not AND) gate
- OR gate
- NOR (not OR) gate
- Exclusive OR (XOR) gate
- XNOR (exclusive NOR) gate
11Digital Logic (continued)
12Digital Logic (continued)
13Digital Logic (continued)
Combining log gates to create a 1-bit binary adder
14Digital Logic (continued)
15Fundamental Components of a Computer
16Fundamental Components of a Computer (continued)
- Computer hardware is any physical device
associated with a computer, such as a keyboard or
monitor - Besides the instructions that users issue through
input hardware devices, computers also receive
instructions via the software stored in its
memory - Software is traditionally defined as a series of
instructions written by computer programmers in a
language that people can understand and that the
computer can translate into binary - The computer must interpret and then execute each
software instruction, again through the use of
its transistors
17Input/Output Devices
- Input and output devices are hardware components
that interface a computer to the outside world - Examples of input devices include
- Mice
- Trackballs
- Microphones
- Web cams
- Styluses
- Touch pads
- Pointing sticks
- Joysticks
- Scanners
18Input/Output Devices (continued)
- Examples of output devices include
- Printers
- Plotters
- Speakers
- Projectors
- Some I/O devices, such as keyboards and monitors,
are integral parts of computers - However, note that not all computers have input
and output devices connected to them - For example, some computers can interface to a
user over a network and do not need their own I/O
equipment
19Central Processing Unit
- The most crucial component of any computer is a
chip called the microprocessor or central
processing unit (CPU) - The microprocessor controls the major
functionality of the computer and is often called
the brains of the computer - The microprocessors many tasks include fetching
a wealth of software instructions, interpreting
and executing these instructions, and storing and
outputting results
20Central Processing Unit (continued)
21Central Processing Unit (continued)
- Key component of the CPU is the control unit,
where instructions are interpreted and control
signals are generated - Based on the result of the interpretation, the
control unit supplies crucial control signals to
other parts of the computer - If the instruction involves the addition of two
numbers, then the control unit issues control
signals to a unit called the ALU, which is
responsible for arithmetic and logical operations
22Central Processing Unit (continued)
- The registers within the CPU are small areas for
temporarily storing information, such as
instructions that are supplied to the control
unit and the results of addition and comparison
operations implemented by the ALU - Software instructions that the CPU interprets and
data that it processes are fetched from a module
called main memory that resides outside the CPU - Unlike main memory, cache memory is internal to
the CPU
23Central Processing Unit (continued)
- Cache memory holds frequently used instructions
and data - Because some software instructions and data are
needed more often than others by the CPU, they
can be stored inside the cache memory and
retrieved when necessary instead of having to be
fetched from the distant main memory every time
they are needed - Saving frequently used instructions and data in
close proximity saves considerable time and
energy
24Main Memory
- Main memory of a computer consists of two types
of memory random access memory (RAM) and
read-only memory (ROM) - RAM is much more prominent it retains its
contents as long as power is supplied to the
computer and loses its contents when the power is
switched off - RAM is also called temporary memory or volatile
memory - ROM, on the other hand, retains its contents even
after power to the computer
25Main Memory (continued)
- Essentially, two types of RAM are used to store
information as long as power is supplied to the
computer static RAM (SRAM) and dynamic RAM
(DRAM) - The contents of dynamic RAM must be refreshed
several times per second, because the electrical
charges representing the bits of DRAM leak out
and must be replenished - There is no need to refresh the contents of SRAM
- DRAMs include transistors and other electronic
components called capacitors that store
electricity, whereas SRAMs are based on
transistors
26Main Memory (continued)
- Although capacitors can store electricity, they
cannot do so indefinitely - Electricity eventually leaks out of them, which
is why it is necessary to refresh the contents of
DRAM - Memory chips that correspond to the main memory
are mostly DRAM - Cache memory within the CPU is typically SRAM
- Due to fundamental differences in how the two
types of RAM are constructed, they differ in
speed, size, and cost
27Main Memory (continued)
- It is faster to save and retrieve the contents of
SRAM, but SRAM is also more expensive and larger
than DRAM - Because cache memory has to be fast, it is better
to use SRAM to build cache memory - DRAM is used within the main memory because it is
the main holding area of the computer and must
have a large holding capacity - Main memory also must be cheap to minimize the
cost of the computer
28Main Memory (continued)
- RAM chips retain ones and zeros that correspond
to instructions and data within small areas
called cells - Each RAM cell can hold one bit of information,
regardless of whether it is DRAM or SRAM - Cells within RAM chips are arranged in rows and
columns - Saving information to RAM is referred to as
writing to RAM, and retrieving RAM contents is
called reading the RAM - Information is written to and read from the RAM
by addressing the RAM cells using addresses
29Main Memory (continued)
30Main Memory (continued)
31Main Memory (continued)
- Although a major part of the instructions that
the computer executes are supplied from RAM, the
computer also relies on some operations based on
instructions stored in ROM chips - ROM chips and RAM chips physically reside at
different places within a computer, but together
they constitute the main memory of the computer - The BIOS chip is an example of a ROM chip found
inside a computer
32Main Memory (continued)
- The major variations of ROMs have historically
included the following - Programmable ROM (PROM)
- Erasable programmable ROM (EPROM)
- Electrically erasable programmable ROM (EEPROM)
- A device that is similar to EEPROM is flash memory
33Storage
- Storage and retrieval of digital information is
one of the most critical components of an IT
system - Without storage, we would have no Web servers,
electronic banking, e-mail, or almost any other
digital application - Storage technologies are discussed later in the
chapter
34Interconnection System
- The physical system that connects I/O devices,
main memory, CPU, storage, and other components
is called the interconnection system - This system is actually a set of wires they are
often grouped together as a set of parallel wires
that transfer signals corresponding to data,
instructions, and control information in an
arrangement called a parallel bus - Some connections do not rely on a set of parallel
wires - Instead, they use a main connection that
transfers bits one after the other, or serially,
from one point to another - Such connections are called a serial bus
35Interconnection System (continued)
36Interconnection System (continued)
- The number of parallel lines within a parallel
bus and the transfer speed of bits across each
line dictate how many overall bits the bus can
carry - The larger the bus width, the quicker the bits
can reach their destination an example would be
the delivery of bits from the main memory to the
CPU
37Interconnection System (continued)
- Types of computer buses include the following
- System busA parallel bus that connects the CPU
and main memory the system bus is also called
the front side bus - Peripheral Component Interconnect (PCI) bus and
PCI Express (PCI-E) busThe PCI bus and its newer
and faster version, PCI-E bus, connect expansion
cards such as network interface cards and sound
cards/adapters - Accelerated Graphics Port (AGP) busThis bus
connects expansion cards called graphics
cards/adapters to the CPU this circuitry
supports computer graphics capabilities
38Interconnection System (continued)
- Expansion cards are connected to the CPU by buses
- They are attached to the buses by being plugged
into special components called expansion slots on
the computers motherboard
39Factors That Affect Computer Performance
- Some of the key factors that affect computer
performance are shown in the following list - Word length
- Bus width and bus speed
- Memory size and memory access speed
- Processor speed
- Instruction set
- Number of CPUs
- Chip set
40Word Length
- Word length is expressed in terms of bits and
corresponds to the maximum number of bits of
information that a computer can process at one
time - The larger the word length is, the faster the
computer - Engineers are constantly striving to design
computers with larger word lengths to achieve
high performance
41Word Length (continued)
42Bus Width and Bus Speed
- Another factor that affects performance is the
bus size, or parallel bus width - Like word length, bus size is measured in terms
of bits - A computer with a large bus width can carry more
bits at a time between computer components, such
as between main memory and the CPU, making it
faster than a computer with a small bus width - Because the buses carry important instructions,
data, addresses, and control signals, the speed
you can gain by using a larger bus width is
important
43Bus Width and Bus Speed (continued)
- The bus size determines how many physical wires
are constructed within the bus - The more wires that designers can incorporate
within a bus, the larger the bus width becomes,
meaning that the bus can carry more bits at one
time - Bus speed, which is measured in hertz (Hz), also
affects computing performance - Even if large bus widths can enable large number
of bits to move between computer components in
parallel, each bus line must also carry bits as
quickly as possible
44Memory Size and Memory Access Speed
- Computers need large amounts of memory for high
performance and multitasking - Because every program occupies some amount of
space in RAM, a large amount of RAM is essential
to operate with multiple programs - Furthermore, RAM size significantly affects
computer speed because information is frequently
written to and erased from RAM - If there is insufficient RAM space, the computer
must frequently resort to using its hard disk,
which results in diminished performance
45Memory Size and Memory Access Speed (continued)
- Other than RAM, the size of the cache memory
(expressed in bytes) is also a consideration - The more cache memory the CPU has, the better the
CPU performs - The speed at which RAM and cache memory contents
are written and retrieved helps to determine
performance - The higher the read/write speed, the faster the
computer is - Typical RAM access speeds are on the order of
nanoseconds (ns), or billionths of a second
46Processor Speed
- The on and off switching of transistors within
the integrated circuits of a computer is managed
by a central digital electrical signal called a
clock - Computer clock speeds are measured in frequency
units called hertz - Just as multipliers are used in the IT world to
express large numbers of bits, multipliers are
used to express large frequency values - 1 kHz 1000 Hz
- 1 MHz 1,000,000 Hz
- 1 GHz 1,000,000,000 Hz
47Processor Speed (continued)
- The higher the clock frequency, the faster the
computer usually is - Typical clock frequencies for modern computers
range from hundreds of megahertz to a few
gigahertz
48Processor Speed (continued)
49Instruction Set
- A computers CPU is typically based on a complex
instruction set computer (CISC) architecture or a
reduced instruction set computer (RISC)
architecture - The difference between them is the number of
clock cycles it takes to execute a single
instruction - Some computer architectures require more cycles
to execute the same instruction than others
50Number of CPUs
- Incorporating more than one microprocessor
increases a computers processing power and speed
because it can use more transistors and perform
multitasking - Some computers have dual-core processors and
quad-core processors - Besides multicore computers, multiprocessor
computers are also available
51Chip Set
- The term chip set refers to a group of chips that
support the microprocessor by controlling the
flow of information between it and other
components, such as the memory chips, graphics
and sound cards, disk drives, and I/O devices - Various manufacturers produce different types of
chip sets, which can significantly affect
computer performance, due to the limitations that
chip sets may impose on memory size, number of
processors, and bus speed
52Inside a Typical Computer
- Some essential components of a modern computer
include - The motherboard
- DVD drive
- Hard drive
- Graphics card
- Sound card
- Network card
- Ports
- Power supply
- Cooling system
53Inside a Typical Computer (continued)
54The Motherboard
- The motherboard is a printed circuit board
(PCB)a planar structure made of resin or other
materials that contains the microprocessor and
many other chips - It also includes the chip set and components that
support the operation of a computer, such as
capacitors and mechanical switches - A PCB supports and interconnects components
through metallic traces called buses printed on
the board
55The Motherboard (continued)
- Other components on the motherboard include
- The BIOS chip
- The chip set
- Slots for connecting RAM modules to the
microprocessor - Default circuitry for supporting sound and
graphics capabilities - Expansion slots for connecting external graphics
cards, sound cards, and network cards - Connectors for attaching hard drives, CD drives,
and other disk drives to the motherboard - Ports for connecting I/O devices such as the
keyboard and mouse
56The Motherboard (continued)
- Boards that carry the RAM chips are called memory
modules, and are connected to the microprocessor
through memory slots on the motherboard - Modern motherboards also come with extra memory
slots to allow users to expand the RAM for faster
processing
57The Motherboard (continued)
- Circuitry for supporting enhanced graphics may
also be incorporated on separate PCBs called
graphics cards or graphics adapters - These types of external graphics adapters connect
to the motherboard via a special expansion slot,
such as the AGP slot - Sound adapters enable a computer to output
high-quality sound - Like graphics adapters, external sound adapters
can be connected to the motherboard via one of
its expansion slots, such as the PCI/PCI-E slots
58The Motherboard (continued)
- Computer networking is all around us, so
motherboards also come with circuitry that
supports networking - Alternatively, network adapter cards may be
plugged into expansion slots on the motherboard - The motherboard also contains connectors and
ports for hard drives, I/O devices such as the
keyboard and mouse, and other devices
59The Motherboard (continued)
60Drives
- Drives are devices that can read and write large
amounts of information to and from various types
of magnetic, optical, or electrical devices, such
as hard disks, CDs, DVDs, and flash memory - If drives are installed in the computer case,
they are called internal drives - If they are connected to the computer externally,
they are called external drives - These drives attach to the motherboard using its
specifically reserved connectors
61Drives (continued)
- One common type of hard drive is the Advanced
Technology Attachment (ATA) drive, which is also
called a parallel ATA drive, an Integrated Device
Electronics (IDE) drive, or an Enhanced IDE
(EIDE) drive - These drives include an integrated component
called a controller, and are attached to the
motherboard via special connectors - Other hard drives include serial ATA (SATA) and
small computer system interface (SCSI) drives,
which also attach to the motherboard via special
connectors
62Drives (continued)
- SATA connections have two advantages over
parallel ATA they can transfer data at a faster
rate between the motherboard and the drive, and
they are more physically compact - SCSI drives are faster than ATA drives, but
because they are more complex, SCSI drives are
not a standard feature of most computers - While internal hard drives connect to the
motherboard with special connectors, external
hard drives attach to the motherboard via
Universal Serial Bus (USB) or FireWire ports
outside the computer casing
63Computer Ports
- Peripheral devices may be connected to a computer
through different types of ports that vary
depending on the type of computer - These ports in turn connect to the motherboard
itself - Some examples of ports include serial ports,
parallel ports, video ports, S-video ports, USB
ports, FireWire ports, sound ports, keyboard
ports, mouse ports, network ports, and telephone
ports
64Computer Ports (continued)
65Power Supply
- A power supply is included within the computer
casing (or externally) to convert the electricity
levels from the wall outlet into levels that the
computer can use - Besides power supplies, other components such as
surge protection systems and uninterruptible
power supplies (UPS) may be employed to safeguard
the computer against sudden surges of electricity
caused by lightning strikes, power outages, and
other phenomena
66Cooling System
- A significant amount of heat is generated by the
many electrical components in a computer, and
problems can arise if these components are not
sufficiently cooled - The chip that generates the most heat is
typically the microprocessor - One popular technique to cool the chip is to
install a metallic component called a heat sink - Another way to conduct heat away from the chip is
to install a fan on the microprocessor or pass
cryogenic materials or other liquids inside tubes
in contact with the microprocessor
67Cooling System (continued)
68Types of Computers and Their Applications
- Types of computers include
- Desktop computers
- Laptops
- Handhelds
- Mainframes
- Supercomputers
- Servers
- Some of these computers may function standalone
or as servers and clients - Some types of servers include e-mail servers,
file servers, and Web servers
69Types of Computers and Their Applications
(continued)
- Servers usually have more than one processor,
considerable memory, and extra hardware - One popular type of server is called a blade
server - Blade servers can be controlled in a computer
network through a remote access card installed in
the server casing - They have the advantage of saving a significant
amount of space they can be housed in remote
locations such as data centers - These servers generate significant amounts of
heat and must be kept properly cooled
70Types of Computers and Their Applications
(continued)
- Thin clients are computers that do not have the
regular hardware typically found on other
computers - They do not have a hard disk or other disk
drives, and they have a scaled-down version of an
operating system stored on a special memory chip - Thin clients rely on other computers over a
network to perform most of their processing
functions - Their major advantage is lower cost due to their
lack of hardware and low power consumption
71Types of Computers and Their Applications
(continued)
72The Future of Computers
- Although transistors have continued to shrink
over the years in accordance with Moores Law,
the trend will not hold true indefinitely - Similarly, wires that connect transistors to each
other continue to diminish in size - This creates a problem as well, because very thin
wires can cause a large loss of energy and limit
the speed by which signals travel over the wires
that constitute computer buses, thereby limiting
the computers speed
73The Future of Computers (continued)
- Alternative technologies are underway, some of
which include - Optical computing
- Optical interconnects
- Nanotechnology
- Carbon nanotubes
- Quantum computing
- Biological computing
74Storage Technologies
- Storage technologies are critical for businesses
to archive and access data, for governments to
store important political information, and for
libraries to store electronic information - Storage schemes initiated with paper punch cards
and paper tapes - Magnetic tapes and disks were introduced later
- Optical and electronic media were introduced last
75Magnetic Storage
- To record bits, a plastic tape, plastic disk, or
ceramic disk is coated with a ferromagnetic
materiala unique material that can be magnetized - The recording material is positioned close to a
writing head that magnetizes small sections of
the medium in one of two directions corresponding
to ones and zeros - A hard disk stores information using the same
principle as magnetic tape, but there are major
differences in their recording formats
76Magnetic Storage (continued)
77Magnetic Storage (continued)
- A hard disk stores bits on a circular disk (also
called a platter) made of highly polished glass
or another material - A typical computer hard disk has many of these
circular disks stacked on top of each other - Each disk stores information on circular tracks
and wedge-like sectors
78Magnetic Storage (continued)
79Magnetic Storage (continued)
- In the case of magnetic tape, information is
accessed serially (sequential access), whereas a
magnetic disk can provide random access to data - Hard disks are limited mainly by their complex
and sensitive mechanics for spinning, writing,
and reading data - Floppy disks are external storage devices that
are not widely used anymore except for file
backups in some legacy systems - Floppies are conceptually similar to hard disks,
but they have a much lower storage capacity
80Optical Storage
- Types of optical storage devices include
- Compact disc-read only memory (CD-ROM)
- Compact disc-recordable (CD-R)
- Compact disc-rewritable (CD-RW)
- Digital versatile disk-read only memory (DVD-ROM)
- Digital versatile disk-recordable (DVD-R)
- Digital versatile disk-rewritable (DVD-RW)
81Optical Storage (continued)
- Bits on optical disks are stored by creating
small areas or domains with different reflective
properties across a long spiral track - Bits are read by shining laser light on these
tiny domains and detecting the light reflected
back from them - Each domain reflects light in one of two ways,
enabling the reader to distinguish between a one
and a zero
82Optical Storage (continued)
- Bits on a CD-ROM are recorded by physically
creating tiny protrusions, also called lands, on
the CDs clear plastic surface during the
manufacturing phase - Areas without lands remain shallow these areas
are called pits
83Optical Storage (continued)
84Optical Storage (continued)
- CDs can record many types of information
- For a device to properly read and save the
information stored on a CD, the device must use
standard formats - For example, music on an audio CD is recorded
following the Red Book standard developed by
Philips and Sony - DVDs rely on the same principles as CD technology
- DVDs can store much more data than CDs, primarily
because the size of lands and pits can be
diminished and spaced in closer proximity, and
because more than one spiral track may be used to
store data due to multiple layers
85Electronic Storage
- Electronic storage, also called semiconductor
storage, has become an extremely effective
technology for quick and efficient information
storage - Electronic storage lets users save data quickly
without the relatively lengthy burn process
required for optical media such as CDs and DVDs - Electronic storage technologies store bits by
trapping electricity within an array of
transistors arranged on a silicon chip
86Electronic Storage (continued)
87Comparing Various Types of Storage Media
- Hard disks provide very fast recording and access
to information and can store large amounts of
data - Because they can be written over and over again
without encountering the limitations of CDs or
DVDs, hard disks are currently the primary
storage medium for computers - Optical disks are portable, lightweight, and can
store information with greater stability than
magnetic media - Optical disks are not affected by magnetic
fields, so they are considered more robust than
magnetic devices, which are prone to data loss
over time - Electronic storage media are compact, fast, and
versatile because they do not contain moving
parts
88Comparing Various Types of Storage Media
(continued)
- Manufacturers can achieve greater capacity by
reducing the physical area occupied by each bit
on the media - However, each storage technology has a limit to
its packing density - On magnetic media, the superparamagnetic effect
causes random fluctuations toward the magnetic
field if bits are packed too closely to each
other - The ability to pack these bits closely on optical
media is governed by the wavelength of light and
the quality of the optics used to focus the laser
beam onto the tracks
89Comparing Various Types of Storage Media
(continued)
- Integrated circuit fabrication technology limits
the density of semiconductor storage devices
because the size of transistors is limited - With advancements in chip manufacturing
techniques, flash memory devices are now
considered to be at the forefront of portable
storage technology - The ultimate limitations of all these storage
technologies have spurred a large amount of
research for alternatives, including holographic
storage and molecular storage
90Summary
- Transistors can be combined to create logic
gates, which can be used as the basic building
blocks for integrated circuits - A computers fundamental components include
input/output (I/O) devices, a central processing
unit, main memory, storage (secondary memory),
and an interconnection system - Factors that affect the performance of computers
include word length, bus width and bus speed,
memory size and memory access speed, processor
rate, instruction set, number of processors, and
chip set
91Summary (continued)
- Components you can expect to find in a modern
computer include the motherboard, CD drive, hard
drive, graphics adapter, sound adapter, network
adapter, ports, power supply, and a cooling
system - Computers come in various types, including
desktop computers, laptops, handhelds,
mainframes, supercomputers, servers, and thin
clients - Future possibilities for computing include
nanotechnology, quantum computing, and biological
computing
92Summary (continued)
- Magnetic media store digital data by magnetizing
a ferromagnetic medium in one of two directions - Optical media store digital data by creating
domains with different reflectivities - Electronic storage media save data by storing
different levels of electrical charge through
transistors - Magnetic tapes are classified as serial access
devices hard disks, floppy disks, CDs, DVDs, and
electronic memory are classified as random access
devices - Possible alternatives for future storage media
include holographic and molecular storage