What is BUS:
The CPU of PC has to send and receive different types of information and data to and from all other devices and components inside a computer and to devices connected to outer extensions of computer.
If we remove the case of CPU then we will see that there is a mesh of wires or electronics pathways connected between motherboard and other components. These are the wires or electronics pathway that joins a variety of components together to commune with each other. This network of electronics pathways is known as ‘BUS’. Thus BUS is simply a set of wires of lines that connects various components inside a computer.
Types of Buses:
Mainly, Computer’s BUS can be divided into two types:
• Internal Bus
• External Bus
Internal Bus: A BUS or set of wires which connects the various components inside a computer, is known as Internal Bus. As it is used for internal communication purposes. It connects various components inside the cabnet, like as CPU, Memory and Motherboard. It is also known as System Bus.
External Bus: A Bus or set of wires which is used to connect outer peripherals or components to computer , is known as External Bus. It allows different external devices to be connected to computer. It is slower than Internal or System Bus. It is also known as Expansion Bus.
Functions of Buses in Computers
The functions of buses can be summarized as below:
1. Data sharing – All types of buses found on a computer must be able to transfer data between the computer peripherals connected to it.The data is transferred in in either serial or parallel, which allows the exchange of 1, 2, 4 or even 8 bytes of data at a time. (A byte is a group of 8 bits). Buses are classified depending on how many bits they can move at the same time, which means that we have 8-bit, 16-bit, 32-bit or even 64-bit buses.
2. Addressing – A bus has address lines, which match those of the processor. This allows data to be sent to or from specific memory locations.
3. Power – A bus supplies power to various peripherals that are connected to it.
4. Timing – The bus provides a system clock signal to synchronize the peripherals attached to it with the rest of the system.
The expansion bus facilitates the easy connection of additional components and devices on a computer for example the addition of a TV card or sound card.
Bus Terminologies
Computers can be viewed to be having just two types of buses:
1. System bus:- The bus that connects the CPU to main memory on the motherboard. The system bus is also called the front-side bus, memory bus, local bus, or host bus.
2. A number of I/O Buses, (Acronym for input/output), connecting various peripheral devices to the CPU -these are connected to the system bus via a ‘bridge’ implemented in the processors chipset. Other names for the I/O bus include “expansion bus”, “external bus” or “host bus”.
Expansion Bus Types
These are some of the common expansion bus types that have ever been used in computers:
• ISA – Industry Standard Architecture
• EISA – Extended Industry Standard Architecture
• MCA – Micro Channel Architecture
• VESA – Video Electronics Standards Association
• PCI – Peripheral Component Interconnect
• PCMCIA – Personal Computer Memory Card Industry Association (Also called PC bus)
• AGP – Accelerated Graphics Port
• SCSI – Small Computer Systems Interface.
