A Depth Knowledge About Processor Internal Structure and Functions


This is an external bus of CPU used for communicate between RAM and Processor through Chipset usualy Northbridge.The Speed of FSB is Measured in MHz or GHz.The faster frontside bus lead to faster overall performance.

Control Unit or CU:

 A control unit works by receiving input information that it converts into control signals, which are then sent to the central processor. The computer’s processor then tells the attached hardware what operations to carry out.

ALU or Arithmetic Logic Unit:

After Getting the control signal from CU An ALUperforms basic arithmetic and logic operations. Examples of arithmetic operations are addition, subtraction, multiplication, and division. Examples of logic operations are comparisons of values such as NOT, AND, and OR.


Registers are the most important components of CPU.There have many types of register presents in a CPU.  Each register performs a specific function. A short description of most important CPU’s registers and their functions are given below.

Memory Address Register (MAR):

This register holds the address of memory where CPU wants to read or write data.

Memory Buffer Register (MBR): 

This register holds the contents of data or instruction read from, or written in memory.

I/O Address Register (I/O AR): 

I/O Address register is used to specify the address of a particular I/O device.

I/O Buffer Register (I/O I3R): 

I/O Buffer Register is used for exchanging data between the I/O module and the processor.

Program Counter (PC): 

Program Counter register is also known as Instruction Pointer Register. This register is used to store the address of the next instruction to be fetched for execution

Instruction Register (IR): 

Once an instruction is fetched from main memory, it is stored in the Instruction Register.

Accumulator Register: 

The accumulator register is located inside the ALU, It is used during arithmetic & logical operations of ALU.

Flag Register

The Flag register is used to indicate occurrence of a ce


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