BUS ARCHITECTURE
In generally, what is a bus and what function is taking? The bus takes the people and languages from one place to another. Is it true? Yes, well. The same way in computer, Bus is a pathway that a computer uses to send data or power from one part to another. Example: CPU to Memory. Buses (show in figure) are characterized by the number of bits they can transfer at a single time.

I'm sure everyone has heard the 8-bit, 16-bit and 32-bit data bus. Well. For example, 8-bit data bus means, transfers 8 bits of data at a time, and a 16-bit data bus means, transfers 16 bits at a time. As a result of increased number of data bus, the processor can receive 4,8,16, and 32 bits respectively. This number known as Bit Size or Word Length of a computer; a computer's bus can be divided into two different types, Internal and External.

The Internal Bus: It connects the different components inside the case: The CPU, system memory, and all other components on the motherboard. It's also referred to as the System Bus.

The External Bus: It connects the different external devices, peripherals, expansion slots, I/O ports and drive connections to the rest of the computer.

In other words, the External Bus allows various devices to be added to the computer. It allows for the expansion of the computer's capabilities. It is generally slower than the system bus. Another name for the External Bus is the Expansion Bus.

We know the bus is just a bunch of tiny wires. One bunch carries info around to the different components on the motherboard, and another bunch of wires connects these components to the various devices attached to the computer. You know that computer takes data from user. Is it true? Yes, well. Data has to be exchanged between devices. Some of the electronic pathways or wires of the Internal Bus or the External Bus are dedicated to moving data. These dedicated pathways are called the Data Bus.

You must note points that the expansion bus, or external bus, is made up of the electronic pathways that connect the different external devices to the rest of your computer. These external devices (monitor, printer, etc.) connect to ports on the back of the computer. Those ports are actually part of a small circuit board or 'card' that fits into a connector on your motherboard inside the case. The connector is called an expansion slot.

Bus width is measured in bits and Bus speed is measured in megahertz (MHz). Now you can ask a question is what is MHz? The megahertz (MHz) is a measurement of how fast some Computer Hardware operates. The different types of buses available, such as following:

Peripheral Component Interconnect (PCI) Local Bus
Accelerated Graphics Port (AGP) Bus
Industrial Standard Architecture (ISA) Bus
VESA Local Bus (VLB)
MCA (Micro Channel Architecture)
EISA (Extended Industry Standard Architecture) Bus
AMR (Audio/Modem Riser) Bus
USB (Universal Serial Bus)
PCMCIA