Question

The system bus includes a control bus, an address bus, and a data bus. Explain why the system bus needs all three buses, and for each of the three buses, explain its role in transporting data.

Answer 1

The system bus is a physical component of a computer system which connects the microprocessor to main memory of the system to carry data between them. The bus provides a path for the data and control signals to move between the components of the computer system.

System bus contains 3 main buses for communication between the CPU, IO and the memory

1. Address Bus: As the name suggest, it is used for the purpose of sharing address between different components of the system. It has following major purpose.

• It used to carry the address that CPU is looking for to the memory and IO devices.
• It is unidirectional as only CPU needs to know which address to look for.
• The size of address bus depends on the capacity of the main memory.
• It does not send back data required by the CPU.

2. Data Bus: To send the data from CPU to memory or back to the CPU we need to have Data Lines.

• It is used to carry the binary data between the CPU, memory and IO.
• It is bidirectional as it sends the data from and to the CPU.
• As it carries the data, so if we know width of a data bus we can determine know what is the word length of the CPU.

3. Control Bus: This is bus through which we can send signals between different components of the computer.

• The control bus is bidirectional
• It is used by CPU to control the synchronization between different component of the computer.
• What type operation is it, is determined by the control signals.
• For every operation we need timing signals and clocks, these signals are also carried by Control Bus.

Hope it clears your doubt :) , and you like it.