Systems Architecture

Systems Architecture

1. Fetch Decode Execute cycle

   • Fetch
     • Fetches instruction from memory such as RAM
   • Decode
     • Instructions is decoded into binary so the computer can understand
   • Execute
     • The CPU performs the actions required by the instruction

2. CPU

   • Clock Speed
     • How fast the CPU can run
     • measured in Megahertz or Gigahertz
     • How many fetch decode execute cycles the CPU can handle in a second
   • Cache
     • the larger the size of the Cache the faster the computer will be
     • the closer the cache is to the CPU the quicker the instructions will be ran
       • Cache has 3 levels each one closer to the CPU
         • level 1
           • Usually part of the CPU itself this makes it the fastest cache level
         • Level 2 and level 3
           • Both of these are slower and take longer to access than L1 and are built between the CPU and the RAM
   • Cores
     • The more cores a CPU has the more powerful it is
       • More cores allows the CPU to run multiple programs at the same time
   • The CPU is an electrical circuit that is responsible for processing the instructions on a computer system

3. Von Neumann Architecture

   • Registers
     • Memory Address Register (MAR)
       • Stores the memory location of data that needs to be accessed
     • Memory Data Register(MDR)
       • Stores the data that is being transferred to and from memory
     • Program Counter (PC)
       • Stores the address of the next instruction to be executed
     • Accumulator (AC)
       • Stores results from calculations
     • Arithmetic/Logic Unit (ALU)
       • Carries out calculations and makes decisions on the data sent to the processor
     • Control Unit (CU)
       • Controls how data moves through the processor and controls the timing of operations and the instructions sent to the processor and the input and output devices

4. Embedded Systems

   • Embedded systems are circuits that have been programmed for a specific purpose and can't be re-programmed to do something else
     • Examples of Embedded Systems
       • Washing machine
       • Car engine
       • MP3 Player

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