Interconnecting the Units of a Computer

CPU sends data, instructions and information to the components inside the computer as well as to the peripherals and devices attached to it. Bus is a set of electronic signal pathways that allows information and signals to travel between components inside or outside of a computer. The different components of computer, i.e., CPU, I/O unit, and memory unit are connected with each other by a bus. The data, instructions and the signals are carried between the different components via a bus. The features and functionality of a bus are as follows—

• A bus is a set of wires used for interconnection, where each wire can carry one bit of data.
• A bus width is defined by the number of wires in the bus.
• A computer bus can be divided into two types—Internal Bus and External Bus.
• The Internal Bus connects components inside the motherboard like, CPU and system memory. It is also called the System Bus. shows interaction between processor and memory.

  Figure Interaction between CPU and memory

  
• The External Bus connects the different external devices, peripherals, expansion slots, I/O ports and drive connections to the rest of computer. The external bus allows various devices to be attached to the computer. It allows for the expansion of computer’s capabilities. It is generally slower than the system bus. It is also referred to as the Expansion Bus.
• A system bus or expansion bus comprise of three kinds of buses - data bus, address bus and control bus.
• The interaction of CPU with memory and I/O devices involves all the three buses.
  • The command to access the memory or the I/O device is carried by the control bus.
  • The address of I/O device or memory is carried by the address bus.
  • The data to be transferred is carried by the data bus.