A maze of the
golden electric circuits etched on the both sides of the motherboard forms
the bus of the computer. A bus acts as the computer system’s expressway.
It transmits data between the various components on the motherboard. Theoretically,
the bus is a collection of wires through which data is transmitted between
the various components of a computer. A bus connects the various components
of the computer with the processor and the main memory. Logically, a bus
consists of two parts, an address bus and a data bus. The data bus transmits
the actual data between the different components on the motherboard, whereas
the address bus transmits the information about which component the data
should be transferred to. A bus transfers data at different speeds like
16-bit, 32-bit, e.g., depending on its width or size. There are two types
of buses depending on the data they transmit, the local bus or the system
bus and the expansion bus or the ‘Input/Output’ (I/O) bus.
The local bus acts as the central bus of the computer. It connects the
processor with the main memory and also with some buffer memory, e.g. the
faster ‘Level Two’ (L2) cache. The other buses connect to the
local bus. The speed of the local bus is measured in the ‘Megahertz’
(MHz). The faster the local bus, better the system’s performance.
A fast local bus allows data to be transmitted faster, thus enhancing the
application processing speed. Previously, all INTEL PENTIUM based computers
used to run on a 60, 66, or 100 MHz system bus. Now, all INTEL PENTIUM
based computers come with the much faster 133, 266, or 400 MHz system buses,
with a promise to deliver much faster bus speeds in the future. The local
bus provides the extremely fast data transfer speeds, but most of the expansion
cards like the display cards or the sound cards on the motherboard process
the data at much lower speeds of about 40 MHz. This leads to certain incompatibility
problems. Therefore, the computers come with a secondary much slower bus
called as the expansion bus. The expansion bus connects the processor to
all other components except the main memory. The data moves along the buses
from one component to another. The speed of the expansion bus is much lower
than that of the local bus. Most new computers come with four main types
of the expansion buses, ‘Industry Standard Architecture’ (ISA),
‘Peripheral Components Interface’ (PCI), ‘Universal Serial
Bus’ (USB), and ‘Accelerated Graphics Port’ (AGP). The
ISA offers the slowest speed.
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