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The system unit of a computer system - Coggle Diagram

- - - - main memroy
        
        Random Access Memory (RAM)
        
        volatile
        
        function
        
        temporiy hold the data and instructions of application software and the operations system
        
        types
        
        Static Random Access Memory (SRAM)
        
        Dynamic Randonm Access memory (DRAM)
        
        Read-only memory (ROM)
        
        functions
        
        store the permanent information suppliesd by the manufacturer
        
        contain the bootstrap program which loads and initializes the operation system of the computer
        
        non-volatile
        
        types
        
        Erasable programmable read-only memory (EPROM)
        
        Electrically erasable programmable read-only memory (EEPROM)
      - Cache memory
        
        high-speed memory
        
        store data and instructions that have been recently used by the CPU
    - - with attributes
        
        word length
        
        Number of bits of data and instructions can handle at one time.
        
        clock rate
        
        Measure speed of CPU
      - executes machine cycle
        
        sub-cycles
        
        execute
        
        Interpret the operation code and perform the required operation.
        
        decode
        
        Identify the operation code and operands in an instruction.
        
        interrupt
        
        end of the execution of an instruction
        
        fetch
        
        Read the next instruction from the main memory into instruction register (IR).
      - contains
        
        registers
        
        control register (CR)
        
        functions
        
        Contain the instructions to be executed by the CPUs
        
        Contains the memory address of the next instruction to be executed
        
        Facilitate the communication of the CPU with the main memory through the system bus.
        
        types
        
        Instruction Register (IR)
        
        Program Counter (PC)
        
        Memory Address Register (MAR)
        
        Memory Data Register (MDR)
        
        General purpose register (GPR)
        
        types
        
        Counter (CX)
        
        Data register (DX)
        
        Base register (BX)
        
        Accumulator (AX)
        
        functions
        
        Load data from main memory into a register.
        
        Store data temporarily in arithmetic operations.
        
        Store data from a register into main memory.
        
        functions
        
        Provide storage space for ALU and CU.
        
        Fastest way for a CPU to access data
        
        Memory units inside a CPU
        
        Status registers
        
        Contain a number of flag bits indicating the status after the execution of instructions
        
        Used in instructions of conditional testing and program branching
        
        control unit (CU)
        
        Keep track of the sequence of instructions being processed
        
        Monitors and coordinates all I/O operations and system units
        
        Arithmetic and logic unit (ALU)
        
        Use registers to hold data during calculations
        
        Results are usually stored in a register called an accumulator
        
        Perform arithmetic and logical operations
  - - - address buses
        
        Transfer the source address or the destination address of data.
      - control buses
        
        Indicate the direction of the data transfer and coordinate the
        timing of the event during transfer.
      - data buses
        
        Transfer data and instructions.