Hardware

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Hardwareand the stupidity of a computer
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Hardware and software

• In order to make a computer do something useful,
  we need both hardware and software
• Hardware The physical parts of the computer
  (monitor, keyboard, mouse and whatever is inside
  the box)
• Software The computer programs (Word, Messenger,
  Counterstrike, Internet Explorer,) we use for
  solving various tasks using the computer

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The computer way

• In order to understand hardware, you need to know
  a little about how a computer thinks
• A computer does not think, it calculates!
• How can you make pieces of metal calculate
  anything useful?

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On or Off

• A computer calculates using metal and current
• A computer can only sense if a current is On
  or Off
• How can we employ this for doing calculations?
• A transistor is used for this exact purpose

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Transistor

• A transistor is a very simple electronic device
• Two wires lead into the transistor, one wire
  leads out
• The smart part The transistor can perform a
  (sort of) calculation, based on whether or not
  there is a current in the two input wires
• A so-called logical function

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A smart (?) transistor

• So, what calculation is that?
• Not so impressive, actually

A B Y
Off Off On
Off On On
On Off On
On On Off
Output
Input
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Logical, right?

• The calculation performed by the transistor is an
  example of a logical function
• A logical funtion takes one or more input values,
  and pro-duces a single output value
• BUT these values can only be either true or false
• Also know as Boolean logic

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Logical functions - example
Output
Two input values
A B Y
false false
false true
true false
true true
Four possible combinations
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Logical functions - example
A B C Y
false false false
false true false
true false false
true true false
false false true
false true true
true false true
true true true
Three input values
Eight possible combinations
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Logical functions - transistor
If we put Off false On true
A B Y
false false true
false true true
true false true
true true false
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Zeroes and Ones

• If we now exchange true with 1 (one), and false
  with 0 (zero), the previous table becomes

A B Y
0 0 1
0 1 1
1 0 1
1 1 0

• This is how we usually denote On and Off
• A numeral system using only 0 and 1 is also known
  as a binary numeral system

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The binary numeral system

• Computers use the binary numeral system (aka
  base-2), humans (mostly) use the decimal numeral
  system (aka base-10)
• In the context of a base-10 system, 110 means
  1x100 1x10 0x1 110
• In the context of a base-2 system, 110 means 1x4
  1x2 0x1 6
• Alternatively
• 11010 1x102 1x101 0x100 110
• 1102 1x22 1x21 0x20 6

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The binary numeral system

• Even if binary numbers appear a bit strange, the
  rules for calculation are the same as for base-10
• In base-10 5 7 12
• In base-2 101 111 1100
• Using a carry works just as before
• 0 0 0
• 0 1 1
• 1 0 1
• 1 1 0, and 1 to carry

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Transistors revisited

• The transistor we saw before was not able to do
  correct binary addition
• However, if you are clever enough, you can
  combine transistors to implement other logical
  functions
• Proper binary addition is just a special logical
  function

11 ?
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Transistors revisited

• The original transistor worked like this

A B Y
0 0 1
0 1 1
1 0 1
1 1 0
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Transistors revisited

• If you combine two transistors, you can implement
  a different logical function

A B Y
0 0 1
0 1 0
1 0 1
1 1 1
A
B
Y
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Transistors revisited

• The combination before was not very useful, but
  we can of course just build more complex
  combinations, involving more transistors
• Our goals is to be able to do binary addition
• Binary addition is just a special logical
  function, taking three input values and producing
  two output values
• Can be considered to be two separate logical
  functions

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Binary addition
A B Carry in Y Carry out
0 0 0 0 0
0 1 0 1 0
1 0 0 1 0
1 1 0 0 1
0 0 1 1 0
0 1 1 0 1
1 0 1 0 1
1 1 1 1 1
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This should do the trick

• Some clever person found out that the below
  combination implements proper binary addition

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The first building block

• We have now found a way to do proper addition,
  using metal and current
• Implementing the other arithmetic operations is
  then not particularly complicated
• This actually forms the foundation for the first
  electronic computers

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ENIAC

• Built around 1945
• Weighs about 30 tons
• Based on vacuum tubes
• Ca. 18.000 transistors
• Used for calculating projectile trajectories
• Was only operational about half of the time

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60 years later

• Today we do not use individual transistors. A
  chip contains a (large) number of transistors
• Most advanced chips contain a few billion
  transistors within an area of perhaps 1 cm2
• What if car technology had progressed at the same
  rate
• Price 1
• Gas consumption 10.000 km/l
• Max speed 100.000 km/h

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Moores law

• Within two years, the number of transistors on a
  chip will double

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From 0 and 1 to Counterstrike

• Even if we can now make metal and current do
  calcu-lations, there is still a very long way
  from 0s and 1s to Counterstrike
• A computer can handle vast amounts of data, at
  vast speeds
• How fast?
• How much data?

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Bits and bytes

• For a computer, the basic unit for data is an
  entity which is either 0 or 1
• This entity is called a bit
• A computer performs operations on bits.
• A more practical unit is a sequence of 8 bits
  this is known as a byte.
• Why 8 bits? Why not 7 or 9? Tradition
• We can for instance define a character set using
  8 bits

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Bits and bytes

• How many distinct bytes are there?
• One byte is 8 bits, each bit is either 0 or 1
• Combinations 2x2x2x2x2x2x2x2 256 (28)
• Each combination can now be interpreted as a
  specific symbol (letter, number, etc), for
  instance the letter H
• With 256 combinations, we have enough
  combinations for capital letters, small letters,
  numbers, etc..
• Example ASCII codes

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ACSII codes
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Amounts of data

• Amounts of data are usually measured in bytes
  (each byte being 8 bits)
• For a computer, all kinds of data are just
  sequences of bits
• It requires a program written by humans to
  interpret a bit sequence as e.g. music, video, a
  Word docu-ment, and so on
• How many bytes does each type of data require?

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Size of some data types
Plain text (no pictures) Music (mp3 format) Video (DVD quality)
Kilo-byte Half a page --- --
Mega-byte 500-page novel One minute One second
Giga-byte Large book-shelf 16 hours 20 minutes
Tera-byte Large library Two years Two weeks
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Speed of calculation

• When a computer calculates, it processes many
  sequences of bits simultaneously
• All calculation units must be syn-cronized for
  this to work properly
• A conductor manages when the calculation units
  should calculate
• The speed of the conductor defines the speed of
  the computer

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Speed of calculation

• How many beats per second (hertz) can the
  conductor manage?
• Old computer (ENIAC) about 10.000 beats per
  second (10 kiloHertz)
• Modern PC about 3.000.000.000 beats per second
  (3 GigaHertz)
• Also known as clock rate

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3.000.000.000 Hertz

• Three billion beats per second is quite fast
• For every beat, light only travels 10 centimeters
• The physical size of the chip begins to matter
• Unfortunately, energy consump-tion rises with the
  clock rate, at a quadratic rate

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CPU

• Where are calculations actually performed?
• Calculations are done in a unit called the CPU
  (Central Processing Unit)
• This unit is basically just one large chip, which
  looks fairly uninteresting

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The CPU and Primary Storage

• The job of the CPU is to perform calculations on
  streams of bits, but who provides these bits?
• Somebody has to feed bits to the CPU, and
  consume the results produced by the CPU
• For this task, the computer uses the Primary
  Storage

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Primary Storage

• A calculation involves the below steps
• Input data is moved from primary storage to the
  CPU
• The CPU performs the calculation
• The result is moved from the CPU to primary
  storage
• The primary storage is thus just a container
  for a certain amount of data
• The primary storage is passive no kind of data
  processing is performed here
• Primary storage is usually of the type RAM
  (Random Access Memory)

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Primary Storage

• What is primary storage physically?
• Just some chips, which contains a certain amount
  of data
• A modern PC will typically have 2-8 Gigabytes of
  primary storage
• What could the data represent? For instance data
  from an mp3-file, for which the CPU must perform
  some calculation to transform it into music

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Primary vs. Secondary

• Primary storage (RAM) has a large advantage
  transfer of data between the CPU and RAM is quite
  fast (several Gigabytes pr. second)
• Fast but compared to what?
• There are however also several drawbacks
• RAM is expensive (compared to what?)
• When power is cut, all data in the primary
  storage will be lost
• We thus also need secondary storage

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Secondary storage

• Who provides data to the primary storage? That
  data is provided by secondary storage
• What is secondary storage? In principle the same
  as primary storage a passive container for data
  - but
• Is much cheaper than RAM (per byte)
• Data is preserved when power is turned off
• Presently, the most common form of secondary
  storage in a PC is a hard drive

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Quite hard(old school)

• A (traditional) hard drive con-tains a number of
  magnetic platters, on which individual bits are
  stored by magnetising a specific area of the
  platter
• A modern hard drive contains 500-2,000 Giga-bytes
  of data

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Quite hard(new school)

• A SSD (Solid-State Drive) hard drive contains a
  number of memory chips, on which individual bits
  are stored in transistors (but retained when
  power is turned off)
• A modern SSD contains 60-500 Giga-bytes of data

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Hard drive vs. RAM
Hard drive (Traditional) Hard drive (SSD) RAM
Typical amount in PC 500-2000 GB 60-500 GB 2-8 GB
Price pr. Gigabyte 0,5 kr. 10 kr. 100 kr.
Data transfer speed 0,1-0,3 GB/sek 0,5-1 GB/sek 4-8 GB/sek
Preserves data without power Yes Yes No
Technology Mechanical Electronic Electronic
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Harddisk vs. RAM

• In other words
• RAM
• Very fast and stable, BUT
• Expensive, does not preserve data without power
• Hard drive
• Cheap, large capacity and preser-ves data without
  power, BUT
• Rather slow, mechanical technology (except SSD)

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Other types of secondary storage
USB-key CD, DVD and Blu-ray Floppy disks Online
Capacity (Gigabytes) 2-256 0,7-30 0,0015 (!) ??
Price (kr pr. GB) Ca. 10 Ca. 1 gt100 ??
Speed (MB pr. sek) 10-100 25 lt 1 Depends on connection
Technology Electronic Optical / Mechanical Magnetic / Mechanical Internet
Note Same tech as SSD Stagnant Almost extinct On the rise
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Motherboard

• A PC contains a board, on which the central
  components of the PC are mounted this board is
  usually denoted the motherboard
• The motherboard will (at least) contain
• CPU
• RAM (primary storage)
• Auxiliary components
• Sockets/slots for adding other components

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Other components

• Examples of other components are
• Graphics card
• Sound card
• Network card
• TV card
• In some PCs, these components are found directly
  on the motherboard, on others they are found as
  extra components, inserted into slots on the
  motherboard
• Why?

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Other components

• Even though a modern CPU is very fast, it may
  benefit from being relieved from certain tasks
• Graphics card
• Specially designed for effective graphics
  calculations
• Takes computational load off CPU
• May increase graphical performance by a factor
  100
• Typical application GAMES!

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Data exchange by bus

• All these units and components need to exchange
  data in order to do their job
• How do they do that?
• Data exchange is done using so-called data buses
• A data bus transports data between two units

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Data exchange by bus

• A data bus sends data
• A number of times pr. second
• A certain amount of data each time
• Example a 32-bit bus running at 100 Mhz
• Carries 32 bit (4 bytes) each time
• Sends 100 million times pr. second
• A PC contains a number of buses running at
  different speeds

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Countryside bus

• A bus is also used for exchanging data with
  additional components, like a graphics card
• Types of buses for extra components
• PCI (Peripheral Component Interconnect) those
  slots in which additional components (such as a
  graphics card) can be inserted
• USB (Universal Serial Bus) used by many
  external devices such as printers, USB memory
  keys, etc..
• Fortunately, buses follow a standard

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External devices

• Devices which enable communication between humans
  and computers
• Typical external devices
• Keyboard and mouse
• Monitor
• Speakers / headset
• Printer
• But also
• Digital camera, phone, USB-key,