Hardware

• Central Processing Unit (CPU)


  The main hardware component that executes instructions and processes data in a computer system
• Computer system


  • Consists of hardware and software
  • Main hardware components: input devices, CPU, primary memory, secondary storage, output devices
• Input devices


  • Keyboard, mouse, game controller, sensors, microphone, webcam
• Output devices


  • Monitor, phone screen, speakers, printer, motors
• Input, Process, Output sequence

  1. Data and commands are inputted by the user using an input device

  2. The CPU processes data by executing instructions

  3. The results are outputted to an output device
• Microprocessor


  A type of integrated circuit on a single chip that contains a central processor designed to perform arithmetic and logic operations
• Microprocessor


  • Contains input/output interfaces and memory
  • Used in a wide range of electronic devices including general-purpose computer systems and embedded systems
• Von Neumann Architecture


  Computer architecture where data and instructions are stored in the same memory (RAM) as binary
• Von Neumann Architecture


  • Central Processing Unit (CPU) fetches instructions from memory and executes them one at a time (serially)
  • CPU stores the results back into memory
• Central Processing Unit (CPU)

  • Has two main components: Control Unit (CU) and Arithmetic Logic Unit (ALU)
  • Control Unit controls the flow of data and sends control signals to components
  • Control Unit decodes instructions into opcode and operand
  • Control Unit controls the timing of operations (clock speed)
  • Arithmetic Logic Unit performs calculations and logical operations
• Special purpose registers in CPU

  • Program Counter (PC)
  • Memory Address Register (MAR)
  • Memory Data Register (MDR)
  • Current Instruction Register (CIR)
  • Accumulator
• Program Counter (PC)


  Stores the address of the next instruction to be fetched from memory
• Memory Address Register (MAR)


  Stores the address of the instruction or data to be fetched from or written to memory
• Memory Data Register (MDR)


  Stores the data that has been fetched from memory or being written to memory
• Components of the system bus

  • Data bus
  • Address bus
  • Control bus
• Data bus


  Transmits data from the CPU to memory or input/output controllers, bidirectional
• Address bus


  Transfers addresses from the CPU to memory, unidirectional
• Control bus


  Transfers control signals from the control unit to other components, bidirectional
• Fetch, Decode, Execute cycle

  1. CPU fetches an instruction from memory

  2. Instruction is decoded into an opcode and an operand

  3. Instruction is executed and the cycle is repeated
• Fetching an instruction


  1. Program Counter holds address of next instruction to be fetched

  2. Address in PC is sent to Memory Address Register (MAR)

  3. Address is sent using address bus

  4. Program Counter is incremented

  5. Instruction is sent from memory address to Memory Data Register (MDR)

  6. Instruction is transferred using data bus
• Instruction Fetch


  1. Program Counter increments

  2. Decode

  3. Execute
• Decode


  The instruction in the Current Instruction Register is decoded, by the Control unit, into an opcode and an operand
• Execute


  The instruction is executed by the Arithmetic Logic Unit and the opcode is performed upon the operand. The result is stored in the accumulator or written to a memory location within memory
• Fetching an instruction using Von Neumann architecture

  1. Program Counter holds address/location of next instruction

  2. Address in PC sent to Memory Address Register

  3. Memory address sent using address bus

  4. Program Counter incremented

  5. Instruction sent from memory address to Memory Data Register

  6. Instruction transferred using data bus

  7. Instruction sent to Current Instruction Register
• CPU Performance can be improved by having multiple cores
• Dual-core processor


  Has two cores
• Quad-core processor


  Has four cores
• Multiple cores


  • Each core runs separate fetch, decode, execute cycles, independently and simultaneously
  • Enables multitasking (running more than one program at the same time)
  • More cores = more instructions executed per second = better performance
• Clock speed


  How many instructions the core can execute each second, measured in Hertz
• Cache


  Small amount of memory situated within or close to the CPU with very fast read/write speeds, used for storing frequently used instructions/data, recently used instructions, and instructions that are to be fetched and executed next
• Doubling the number of cores does not necessarily mean double the number of instructions executed per second
• Instruction set


  List of all the commands that can be processed by a CPU, each with a unique binary code
• Instruction lists are machine-specific, so a program created using one computer's instruction set would not run on a computer containing a processor made by a different manufacturer
• Embedded system


  Computer system with either one function or limited specific functions, built within a larger mechanical device, to control the device and allow user interaction
• Types of embedded systems

  • Microcontrollers
  • Microprocessors
• Microcontroller


  Integrated circuit containing a CPU and memory (RAM or ROM) built in to the same chip
• Microprocessor


  Integrated circuit containing only a CPU on the chip, with RAM, ROM, and peripherals needing to be added
• Embedded systems often have firmware which is software built into the system and cannot be reprogrammed by the user
• Head to www.savemyexams.com for more awesome resources
• Advantages of embedded systems

  • Low power consumption
  • Small physical size
  • Low cost to manufacturer
  • Can be controlled remotely
  • Can operate in real time and respond to inputs very quickly