Grade 11

1
Grade 11

• Computer Architecture
• Chapter 1
• pg1

2
The Motherboard

• Important components on the board are
• CPU
• RAM chips
• ROM chips
• Buses
• Cache memory
• Slots for cards and connectors
• System Clock
• AGP video slot
• USB port connectors

3
Motherboard

• The motherboards main purpose
• To control some of the other parts of a computer
• To provide a way by which the parts of the
  computer can communicate with each other

4
Primary memory

• Primary memory is
• Used to store the operating system, program
  instructions (applications) and data in use
  whilst the computer is running
• Electronic and has no mechanical parts that can
  break down
• Memory that can operate at very high speeds

5
Static RAM

• Uses two transistors does not need continuous
  refreshing
• Capable of responding to the read write requests
  faster than DRAM

6
Dynamic Memory (DRAM)

• Semi conductive memory uses capacitors to store
  data
• The capacitors store either a low or high voltage
  in order to register a 1 or 0
• The time that the capacitor can store its charge
  is directly related to its size

7
ROM

• Read Only Memory
• It generally cannot be written to and
• It holds its contents even when the power is off

8
Types of ROM

• Regular ROM
• Programmable ROM (PROM)
• Erasable Programmable ROM (EPROM)
• Electrically Erasable Programmable ROM (EEPROM)

9
Regular ROM

• Constructed from hard wired logic much like the
  processor
• It is designed to perform a specific function and
  cannot be changed
• Generally only used for programs that are static
  and mass-produced

10
Programmable ROM (PROM)

• Can be programmed using special equipment (ONLY
  ONCE)
• Similar to the way a CD-ROM recorder works by
  letting you burn programs onto blanks once then
  letting you read from them many times

11
Erasable Programmable ROM (EPROM)

• Can be erased and reprogrammed
• A Perspex window is installed in the top of the
  ROM package
• This holds the memory
• Ultra violet light can be shone through the
  window to erase the EPROM

12
Electrically Erasable Programmable ROM (EEPROM)

• Can be erased under software control
• Most flexible type of ROM
• Frequently used for holding BIOS programs
• Flashing the BIOS refers to reprogramming the
  BIOS

13
Cache memory

• A special high speed memory (static RAM) reserved
  for temporary storage of the data or instructions
  likely to be needed next by the processor

14
BUSES

• What is a bus?
• An electronic path way along which signals can be
  sent from one part of a computer to another
• Types of buses
• Data bus
• Address bus
• Control bus

15
Data Bus

• The data bus is the way that data and programs
  instructions travel to the CPU

16
ADDRESS BUS

• When the CPU needs data or instructions from
  memory, it has to tell memory where the
  data/instruction must come from.
• The address bus carries this address.

17
Control Bus

• Carries control signals , the signal that tells
  memory if the CPU wants to read or write memory.

18
Operation of the CPU

• The CPU deals with each instruction in a series
  of steps these steps are repeated for every
  instruction that gets processed so the series of
  steps is called a cycle.
• This cycle is called the machine cycle

19
Machine cycles

• Each machine cycle involves
• Fetching an instruction from memory
• Decoding the instruction
• Transferring data
• Executing instructions

20
The Central Processing Unit (CPU)

• The brain / working part of the computer

21
Components of the CPU

• All CPUs are divided into parts that do specific
  jobs. The main components are
• Control Unit (CU)
• Arithmetic Logic Unit (ALU)
• Registers
• Cache

22
The Control Unit

• One of the most important
• In charge of entire processing
• Performs its job by repeating what is called
  machine cycle
• Creates control signals that tell the ALU and the
  register how to operate
• Makes sure everything happens in the right place
  and time

23
Arithmetic logic unit (ALU)

• Responsible for all mathematical and logical
  (comparative and decision making) aspects of the
  computer operation

24
Registers

• A register is a storage area within the CPU
• Both the CU and ALU contain registers
• Used to hold the addresses of instructions and
  data in memory
• Hold the data that the CPU is currently working on

25
Registers

• All data must be represented in a register before
  it can be processed
• Some registers are used for specific tasks
• The program counter contains the address of the
  next instruction to be fetched and executed
• The instruction register is used to hold the
  instructions being executed
• The address register is used to hold the address
  of data to be used

26
Cache

• All CPUs have at least L1 cache and most have L2
  cache built into them.
• Cache is another form of storage designed to
  enhance the speed of the whole computer system by
  keeping the CPU supplied with date and
  instructions all the time

27
The machine cycle (HG ONLY)

• The instruction to be executed is fetched from
  memory to the CPU
• The control unit decodes the instruction
• Data is transferred
• The instruction is executed

28
Modular PC design

• This means that a computer board is not designed
  as one solid unit but is made up of many parts
• Modules are easy to change and interchange
• Upgrading cheaper and easier than buying a single
  component computer

29
Modular design

• The modules include
• Motherboard
• RAM
• ROM
• CPU
• Controllers

30
Controllers

• Not all controlling circuitry has to be on
  separate cards that plug into expansion slots
• Expansion cards are separate boards containing
  circuitry to control peripherals such as screens
  or speakers

31
Expansion cards

• Provide functions which are separated from the
  system board and provide expansion capability to
  the PC

32
PCI

• PCI slots are on the motherboard and allow you to
  plug expansion cards into the board

33
ISA Expansion slots

• ISA slots are on the motherboard and allow you to
  plug older expansion cards into the board

34
PORTS

• The circuit board must provide some way for
  peripheral to connect to the computer and this is
  called a port

35
Serial and parallel port

• Found at the back of the computer case and are
  used to connect peripherals such as printers or
  the mouse
• 3rd port is standard on new computers called a
  USB port

36
More about ports

• There are two traditional ports in use in all new
  PCs namely the COM port and the LPT port

37
COM Ports

• Serial port most frequently used to connect a
  mouse or an external modem to your computer
• Serial port used is usually RS 232C port

38
LPT Ports

• A parallel port which is most frequently used to
  connect the PC to a printer
• Older LPT is the Centronic port, but most new PCs
  allow the LPT port to be specified in the BIOS
• SPP- old Centronic LPT port
• ECP (Expanded Capabilities Port) and EPP
  (enhanced Parallel Port)
• Bi directional communication
• 10 times faster than SPP

39
Universal Serial Bus (USB) Port

• New serial port allowing up to 127 devices to be
  connected to one port
• Plug and play
• Hot swappable

40
Wireless connection

• Most common is called BLUETOOTH
• Wireless networking connection based on very high
  frequency radio signals with a short range (10
  15 meters)
• Allows various electronic devices to talk to each
  other without physical connection
• Without user intervention
• Through walls

41
Video performanceVideo cards

• Contains a video encoder that converts a digital
  representation of the screen into an analogue
  signal to be sent to the monitor. The picture is
  created by the CPU

42
Video Performance2D accelerators

• Contains the same as Std Video a processor and
  programs (in the ROM)to allow the card to draw
  some of the picture that the CPU would have to
  draw

43
Video Performance3D accelerator cards

• Contains the same as the 2D card powerful
  processor and lots of RAM to be able to render
  3D objects that usually would have to be created
  by the CPU

44
AGP ( Advanced Graphic Port)

• Faster video performance
• Single slot on a pentium II, III and IV
  motherboard for use with AGP graphic cards only
• AGP graphics cards can transfer data _8 times
  faster than a graphics card plugged into a PCI
  slot

45
VRAM

• Video Ram

46
Video Capture Cards

• Allows you to capture and edit video
• Video capture requires a special add on board
  called a video capture card.
• Because of large amount of data, should only be
  attempted on very fast computers with large
  amounts of RAM and disk space

47
Sound Cards

• Add on card that plugs into the expansion slots
  of the PC and enables the PC to produce sounds
  beyond the normal beeps of the standard PC
• Does two basic jobs
• Plays back recorded sound. Recorded in digital
  format stored as .wav file
• It synthesizes the sound of musical instruments

48
Hard Drive

• Consists of platters coated with magnetically
  sensitive material.
• Each platter has two read-write heads (one for
  each side)
• Heads are attached to a single access arm which
  means they cannot move independently
• The platters spin continuously whilst the
  computer is in use.

49
Determining hard drive speed

• Spin does not determine the speed
• The speed is determined by two criteria
• The access time of the hard drive
• The data transfer rate of the drive

50
Structure of a disk

• The hard drive needs a structured layout so that
  data can be stored on it
• Platter and Head
• The first platter is always called platter 0
• The first head (usually the top one) is called
  head 0

51
Tracks and sectors

• Concentric circles around the heads are called
  tracks
• These tracks are further divided up into pie
  shaped sectors The number of sectors depends on
  the density of the disk.
• On hard drives the sectors are grouped into
  clusters

52
Access time

• How long it takes to locate a single piece of
  information and make it available to the computer
  for processing
• The mechanical arm must first move the read/write
  head to the desired track or cylinder

53
Hard drive controller

• Electronic circuit board responsible for telling
  the hard drive to go to a specific address and to
  read the information stored there

54
IDE

• Nothing more than an interface.
• The controlling circuits for the hard drive are
  built onto the hard drive
• The IDE just allows the drive to communicate with
  the CPU/memory in a standard way
• The IDE controller is simply the standard
  interface that all IDE hard drives must be
  compatible with