James Tam

Introduction to hardware

Concepts covered

•Units of measurement

•Processors

•Memory

•Input and output

•Storage

•Peripherals

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Basic units of measurement

Bit

•binary digit

•smallest unit of measurement

•two possible values

Byte

•8 bits

Word

• The number of adjacent bits that can be stored and manipulated as a unit

•32, 64 for home computers, 128 for the most powerful

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Large units of measurement (storage size)

Note: use powers of two because computer storage (bytes) are based on the basic unit (bit).

~ 20 million four-drawer filing cabinets full of text

Kilobyte (kB) – a thousand bytes (1,024 = 210)

Megabyte (MB) - a million (1,048,576 = 220)

Gigabyte (GB) – a billion (1,073,741,824 = 230)

Terabyte (TB) – a trillion (1,099,511,627,776 = 240)

Petabyte (PB) – a quadrillion (1.125899906843e+15 = 250)

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Small units of measurement (speed)

millisecond (ms) – a thousandth of a second (1/1,000 = 10-3)

microsecond (μs) - a millionth of a second (1/1,000,000 = 10-6)

nanosecond (ns) – a billionth of a second (1/1,000,000,000 = 10-

9)

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What is hardware?

Hardware includes the physical components of a computer system e.g., a monitor, keyboard, mouse and the computer itself.

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High level view of the hardware in a computer

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Processor

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Processor

The brains of a computer (maybe not…)

A real processor

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Processor speed

Determined by many things

•Type of processor

•Clock speed (as measured in Hertz e.g., MHz, GHz)

* But also consider the rest of the computer!

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Relationship between clock speed and times between pulses

Examples

1 Hz = 1 pulse is sent out each second (1 second passes between each pulse)

10 Hz = 10 pulses are sent out each second (0.1 seconds passes between each pulse)

:

25 MHz machine = 25 million pulses sent out each second (0.000 000 04 seconds between each pulse or 40 ns between pulses)

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Some common types of processors

Intel processors (usually run some version of MS-Windows)

Type of processor Clock speed

Celeron 500 MHz – 1.3 GHz

Pentium III 650 MHz – 1.2 GHz (1200 MHz)

Pentium IV 1.4 GHz (1400 MHz) – 2.2 GHz (2200 MHz)

PowerPC processors in Apple computers

Type of processor Clock speed

G3 500 MHz – 700 MHz

G4 733 MHz or 867 MHz

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CISC processors and RISC processors

CISC (Complex Instruction Set Computers

•e.g., Pentium; 68000, 68020…(old Apple computers)

RISC (Reduced Instruction Set Computers)

•e.g., PowerPC (new Apple computers)

Difference

•Instructions on RISC computers are simpler?

•Architecture differs between the processors.

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Memory

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Types of memory

1) RAM

2) ROM

3) Caches

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1) RAM (Random access memory)

Often used for short term storage of information

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Characteristics of RAM

Volatile

Used for temporary storage

Typical ranges 128 MB ~1 GB

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2) ROM (Read only memory)

You can read but not change the contents

Contents written to (burnt) by special equipment

Non-volatile

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Types of ROM

•ROM

•PROM

•EPROM

•EEPROM

•Flash Memory (e.g., a computer BIOS, memory for game consoles)

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3) Cache memory

Stores less than RAM but much faster

Can be either part of the processor (L1) or separate from it (L2)

Both are much faster than regular memory RAM

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Input

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Input devices

Used by a person to communicate to a computer.

Person to computer

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Common input devices

Keyboard

Mouse

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Output

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Output devices

Displays information from the computer to the a person.

Computer to a person

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Most common output device

A computer monitor

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How many monitors work

Images are displayed with dots (pixels)

Picture from Beekman

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Quality of monitors determined by

1) Size

2) Resolution

3) Color depth

4) Dot pitch

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1) Monitor quality (size)

Measured diagonally

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2) Monitor quality (resolution)

Columns of pixels x Rows of pixels

Col 1, Row 1

Col 2, Row 1

Col 3, Row 1

… Col [c], Row 1

Col 1, Row 2

Col [c], Row 2

Col 1, Row 3

Col [c], Row 3

: :

Col 1, Row [r]

Col 2, Row [r]

Col 3, Row [r]

… Col[c], Row[r]

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3) Monitor quality (Color depth)

The number of possible colors that can be displayed for each pixel.

e.g. monochrome (single color) 01

2 possible values

Uses up 1 bit of space

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3) Monitor quality (effects of color depth)

16 million colors256 colors

16 colors2 colors

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Tradeoff between resolution and color depth

There is a limit for both

e.g. 16 bit color at 1600 x 1280 = 2 bytes per pixel * 1600 columns of pixel * 1280 rows of pixels = 4.096 MB

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4) Monitor quality (dot pitch)

Dot pitch is the distance between the center of each color dot (mm)

3 guns form 1 color dot

dot pitch

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Refresh rate of monitors

How fast the screen is redrawn

Again there is a tradeoff between resolution and refresh (70 Hz / 70 times per second is usually a good minimum)

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Types of monitors

1) CRT – use three electron guns (shown on previous slides)

2) LCD (flat screen) – use a liquid crystal display

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CRT’s vs. LCD’s

CRT

•Cost less for the same quality

•Sharper images possible (more colors, higher resolution)

•Can view images from any angle

LCD

•Less eye strain (no flicker and less glare)

•Uses less space

•Use less power

•Weigh less

•Lower radiation

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Storage

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What is the difference between storage and memory?

Memory

•keep the information for a shorter period of time

•faster

•more expensive

•“scrap paper for the computer”

Storage

•the information is retained longer

•slower

•cheaper

•“file cabinet for the computer”

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Types of storage

1) Optical

• CD-ROM

• DVD

2) Magnetic

• Hard drives

• Floppy disks

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1) Optical CD & DVD

CD ROM (read only)

CD-R: needs a CD-burner to create (record) to a CD

•Cheap and portable storage of a lot of data (650 MB)

CD-RW: can write and erase CD to reuse it (rewritable)

DVD-ROM (DVD-ROM/RW’s) – stores even more info

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1) CD’s and DVD’s (recording information)

Use special compounds

By default the surface of the CD is reflective

CD

A weak laser (read laser) is shot at the disc to determine the reflective portions

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1) CD’s and DVD’s (recording information)

A strong laser (write laser) heats selected parts of the disc.

CD

The melted part no longer reflects light

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1) CD’s and DVD’s (erasing the information)A laser (erase laser) heats selected parts of the disc (not quite as hot as a write laser).

CD

The re-melted part reflects light again

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2) Magnetic drives (hard drives)

Stores a lot of information (~20 GB – 80 GB)

Slower than memory (but faster than other forms of storage)

Spin rate (5400, 7200, 10000 rpm)

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2) Magnetic drives (floppy)

Pros

•Portable

•Cheap

Cons

•Slow

•Low storage capacity (1.44 MB)

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2) Magnetic drives (structure)

Platters (hard drives only!)

Tracks (inside circles)

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2) Magnetic drives (structure)

Sectors (wedges)

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2) Magnetic drives (structure)

A cylinder (a bunch of sectors on different platters, one on top of the other – hard drives only)

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Motherboard (Systemboard, Mainboard)

Many parts of the computer are attached to it.

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Buses

Connects together the different parts of the computer.

Used for the transfer of information.

Width determines its speed

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PortsAre used to connect the computer to outside devices

Serial, parallel

•Ports on older computers (slower, 1 port to one device)

USB (Universal serial bus)

•Standard on newer computers (faster, up to 127 devices on 1 port)

Firewire

•Fast (video)

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Printers

Allows text or graphics to be printed out on paper

Common types

•Inkjet

•Laser

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How inkjet printers work.Use a series of nozzles to spray drops of ink directly on the paper

Printer heads

Ink nozzles

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Characteristics of Inkjet printers

Printer costs less (black and white ~ $70.00, color ~$100.00+)

Cost per page is more

Slower

Text is lower quality, color pictures may be higher quality

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How laser printers work

Use a laser to produce patterns on an ink drum using static electricity

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Characteristics of Laser printers

Printers cost more (black and white ~ $300.00+, color ~$3000.00+)

Cost per page is less

Faster

Text is higher quality, color pictures may be lower quality

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Some other peripherals

Scanners Cameras

Speakers Joysticks

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SummaryImportant concepts

•What is hardware and what are common units of measurement used

•Processors – what do they do, what are their characteristics, types of processors

•Memory – what is it, types of memory

•What is the purpose of an input device, types of input devices

•What is an output device, types of output devices

•General characteristics of computer monitors

• Storage devices – different types and how they work

•Other parts of a computer (beyond the simple model) – motherboard, buses, ports

•Common peripherals (printers, scanners, cameras)