systems architecture

systems architecture

1. fetch, decode, execute

   • fetch
     • fetches the information from the RAM
     • Address
       • the address is generated by the program counter (PC) and is transported along Address busses to the Memory Address Register
   • decode
     • load from RAM
       • the information is decoded into the opcode 0101 into a LOAD FROM RAM instruction
     • why the computer decodes
       • used so the computer can see what the instruction wants it to do, e.g. add, store, switch, repeat ect.
   • execute
     • after it is decoded the information is executed
     • performed by CPU
     • if instruction
       • it will control all input and output and the control unit will deal with it
     • if calculation
       • then the arithmetic logic unit will deal with it and the results of any equation are stored in the accumulator

2. memory

3. performance of the CPU

4. main parts of the computer are...

   • Arithmetic/Logic Unit (ALU)
     • Carries out calculations and makes decisions on the data sent to the processor 
   • Accumulator (AC)
     • stores results from calculations
   • Program Counter (PC)
     • stores the address on the next instruction to be executed
   • 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 (I/O) devices.
   • Memory Address Register(MAR)
   • Memory Data Register (MDR)

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