Computer Science Questions and Answers: General Structure of CPU Part - 6

1. Explain the General Structure of CPU.
Program counter: This register stores address of next instruction to be executed. Memory address register (MAR): This register specifies address in memory where information can be found. This register is also used to point to a memory locations where information can be stored.
Memory buffer register: This register acts as an interface between CPU and memory. When CPU issues a Read Memory command, instruction is fetched and placed in MB register.
Instruction register: This stores a copy of current instruction.
Instruction decoder (ID): ID is an electronic hardware, which decodes instructions. The instructions are further broken down into a set of micro operations, so that they can be executed directly.
General purpose registers: They are used to store data. There are 6 GP registers. These are used for storage of data as needed by the program.
Arithmetic logic unit: The basic arithmetic operations such as addition,subtraction,multiplication and division are carried out here. These operations need atleast two operands, one which is stored in accumulator and the other in the MBR. After the manipulation of data in ALU, the result is transferred to accumulator.
Accumulator: During processing the intermediate data needed for future processing is stored in accumulator. The contents of ACC are used by ALU for operations and later by MBR holds the final result for further action.