Test Revison

Test Revison

1. System Architecture

   • Purpose of CPU
     • To coordinate and carry out the fetching, decoding and execution of instructions.
   • Fetching instructions
     • Instructions are copied from main memory into the processor
   • Von-Neumann architecture
     • Characterised by instructions and data in RAM. One instruction is fetched, decoded and executed at a time
   • CPU Register
     • Small, fast are of memory in the CPU that has a specific purpose
   • MAR (Memory Address Register)
     • Stores address of where to fetch instructions/data from the RAM
   • MDR (Memory Data Register)
     • Stores data or instruction fetched from RAM
   • PC (Program Counter Register)
     • Stores address of the next instruction to fetch from RAM. Increments by 1 unless instructed otherwise.
   • Accumulator
     • Stores the result of a mathematical operation
   • ALU (Arithmetic Logic Unit)
     • Performs mathematical sums and Boolean logic comparisons.
   • CU (Control Unit)
     • Controls the execution of instructions. Some CPUs have multiple coeres
   • CPU Cache
     • Stores most recently used/pre-empted instructions to speed up the fetching of instructions as cache is faster than RAM, slower than registers