Data Bus, Address, Control, System, Expansion, ISA, PCI, AGP Bus

Data Bus, Address, Control, System, Expansion, ISA, PCI, AGP Bus

Data Bus, Address, Control, System, Expansion, ISA, PCI, AGP Bus


A computer system consists of different parts and different devices you must be able to communicate with other devices, all devices are connected together by a communication channel called but. A bus consists of that of communication lines are wires it is used to move a large amount of data in the form of electrical pulses from one part of the computer to another.

There are different parts of the computer that must communicate with each other.

  1. Control unit
  2.  Arithmetic and logic unit
  3.  Main memory like RAM and ROM
  4.  Input and Output devices

Buses are basically designed by a different electrical parallel structure connected with another. But is a common path to transfer data and information between the CPU main memory and other parts of the computer is called a bus. It is also used to transfer and send data from secondary storage like the hard disk. The capacity of the bus depends upon the number of data lines are things in it the amount of data that was can transfer at a time is called bus with a bus with 16 lines can carry a 16 bit of data and a bus with the 32 lines can carry 32 bit of data. All the buses are part of the motherboard.

The speed of the bus at which data move from one part of the computer to another is called up the bus clock speed. The bus speed can we measure in the clock speed. It affects the overall performance of the computer system,  but it has a unit is called megahertz are millions of clock cycles per second. Basically buses are used for the interconnection of different parts their different advanced technologies are used nowadays. Normally help the different part of a computer communicate with each other for transferring of data and information

Advantage of Computer Buses

  1. The bus is used for the communication of the different parts of the computer that allows the different to transfer data at high speed or increase the speed of the computer
  2. If the computer design has multiple buses the overall performance the computer will be improved

 Disadvantages of Computer buses

  1. The basic disadvantage of the first network bus is if the main bus fail the whole network will be damaged
  2. If the main cable was filled all performance will be affected.

System buses

Different  type of System buses are as follows

  1. Date bus
  2. Control bus
  3. Address bus

Data bus

Data bus is the common type of the system bus, It is used to transfer data from one components to another. It is an electrical path that connected the CPU memory and input-output devices and also secondary storage devices. Data bus consists of different parallel lines. A bus with more lines can transfer a large number of data. A bus with 16 lines can transfer 16 bits of data if the bus contain 32 line it transfers 32 bit of bus. In old computers the data bus is used to transfer the only one byte of data at a time. But nowadays our data bus in our modern computer can be used to transfer a more data that improve the speed and performance of the computer system data bus design in such a way that allow all the components to communicate with each other efficiently.

Address Bus

The address bus is used to carry the address from one component to another. it also consists of different wires like a data bus. It is used to connect the central Processing Unit (CPU) and main memory, and main memory like RAM. When the CPU wants to transfer the data to the main memory and take the data from the main memory following steps are performed.

  1. CPU put the address of required data on the address bus
  2. The address has carried the address to the main memory
  3. the data from the main memory cache according to the address and put on the date bus.
  4. Then that carry the data to the CPU

the performance of the bus depends on the number of lines. The total number of determine the performance of the bus if the address bus has the eight lines the maximum number of is 256. In modern computer there are 32-bit address bus is used this computer can access 4 GB of data from main memory like RAM.

Control Bus

This type of bus is used to transfer an address from one component to another. If the CPU wants to read data from the main memory or write data to the main memory.CPU can send a signal on the control was like a memory read our memory write If CPU wants to read data from the main memory put the signal of reading data on the control bus and if the CPU wants to write that on the main memory signal memory Write on the control bus.

The control bus is also used to transmits another type of signal like ACKS(acknowledgment single).

There are some terms that are using in the control bus are as follow

  1. Timing Information:  it specifies the time for which a device can use data and address bus.
  2. Command Signal: it defines the type of operation to be performed by CPU.

For example, the CPU gives a command to the main memory to write data.

The following steps will be performed.

  1. Cpu pit the address of data, where it writes in memory.
  2. Put the data on the data bus.
  3. put the signal on the control bus write data..

After writing the data process memory sends acknowledgment signal to CPU.

when CPU receive that single it will not perform than another task

Expansion bus

A type of bud that used to connect the CPU with other devices like I/O devices is called the expansion bus. These buses usually consist of 15 and 64 bit. These buses are placed on the motherboard. This is also used to connect the CPU to the expansion slot on the motherboard to which external devices may be connected. All the expansion buses provide access to the processor to communicate with the external devices.

These buses provide the fastest transfer of data transfer data at a high speed,

Types of Expansion buses

a different type of expansion dresses are as follows

ISA bus

ISA stands for industry-standard architecture. it was introduced in 1984.

It is developed by IBM for the personal computer. It is the most common type of expansion bus. Its speed is very slow. These buses are used to transfer data 8 bits at one time. Mouse and sound card that required the Slow speed network connected through ISA.


PCI bus speed is more than Industry standard architecture bus. PCI bus design to fulfill the video demand of the graphical user interface. PCI is the high speed reduced to transfer 32 bit or      64 bit of data or 20 times faster than the ISA bus.

AGP bus

AGP stands for Accelerated Graphics Port. It is developed for the acceleration of graphic performance. It is much faster than the PCI bus it is basically used to improve the speed of 3D graphics and video transmit. it considered as a faster interface between the video card and memory. all its first speed is to replace the PCI bus for the video data.


USB stands for Universal serial bus. A USB device can be attached to the computer to a single USB port. USB used connect with computer through a single port. It is used to store the highest video capturing devices and scanner etc

PC card bus

PC cars design for transferring data between CPU and PCI bus. It is designed for PC cards.

Prof. Fazal Rehman Shamil
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