Topic 3: Computers

Topic 3: Computers

1. Von Neumann Architecture

   • CPU
     • Components
       • The Control Unit
         • directs data around the system and sends instructions to other components, for example it sends control signals to memory to put it in read or write mode
       • The Arithmetic Logic Unit (ALU)
         • carries out mathematical and logical operations such as addition, subtraction, AND and OR operations
       • The Registers
         • provide quickly accessible storage within the CPU e.g. when some data is fetched from memory, it will be stored in a register before being sent to the ALU for processing
     • Fetch, decode and execute instructions from memory
     • Clock Speed
       • how many instructions the computer can execute per second
       • Clock speed is measured in hertz (Hz) which means per second
   • Addressable Memory (RAM)
     • Addressable memory contains the instructions and data required by the CPU, arranged into sections, each with a numerical address
   • Busses
     • Data Bus
       • Used to transfer data to and from the memory location indicated by the address bus
       • Bi-directional data is sent both ways
     • Address Bus
       • Used by the CPU to send the memory address of the location to be read or written to
       • Uni-directional addresses are only sent from the CPU to memory
     • Control Bus
       • Used to transfer control signals between the CPU and memory, such as whether to use read or write mode, or error codes
       • Bi-directional control signals are sent both ways

2. Secondary Storage

   • Magnetic
   • Optical
   • Solid State
   • Virtual Memory

3. Embedded Systems