CPU (Central Processing Unit)

CPU (Central Processing Unit)

1. Parts

   • Control Unit (CU)
     • Acts as a organizing force of the computer
     • Is in charge of ...
       • Controlling the sequence of the execution of instructions
       • Moving information between the CPU and the Primary Memory via Data Bus
       • Controlling the Cache Memory
         • Cache Memory stores the instrucions that are used many times
     • Works with Special Registers
       • Memory Address Register (MAR)
         • Stores address of the data that was fetch to the CU
         • Stores address of where the data that was fetch to the CU is stored in the Cache Memory or in the RAM
       • Memory Data Register (MDR)
         • Stores Information that has being fetch or needs to be store inside the addresses that are store by the MAR
           • Both are used in the Machine Cycle
       • Program Counter (PC)
         • Contains addresses of the instructions that are going to be executed next by the IR
       • Instruction Register (IR)
         • Holds instructions that are being executed
     • Takes place in the Machine Cycle, by doing the process of fetching and coding
     • It doesn't execute instructions
   • Arithmetic and Logic Unit (ALU)
     • Performs ...
       • Logical operations
         • AND - OR - NOT
       • Arithmetical operations
         • Adding - Multiplying - Dividing - Subtracting
     • Receives instructions decode by the CU

2. Machine Cycle

   • Process in which a instructions is executed
     • 4 Main Steps
       • 1. Fetch
         • 2. Decode
           • 3. Execute
             • 4.Write-Back
               • Done in the ALU
               • Outputs the executed instructions into the RAM or the Cache Memory by the use of Data Bus
             • Executes the instructions and gets more information if it is necessary
         • Done in the CU
           • 2. Decode
             • Brakes the instructions into parts and sends it to the ALU by the use of Data Bus
         • Search for a instructions in the RAM or the Cache Memory, that comes with a Address that is save by the MAR

3. Can transfer information (Instructions or Addresses - Data) between them and the rest of the components in the computer by the use of Buses

   • Address Bus
     • Tranfers addresses
   • Data Bus
     • Transfers information