BUS Configurations

 

Objectives:

To describe some of the main bus technologies and configurations, and to discuss
the plug-and-play system

discuss the function of buses

describe the most common bus standards available

outline how buses typically relate to one another in a modern PC

outline the concept and the practicalities of the plug-and-play system

 

Lesson:

 

The modern PC generally contains several buses rather than a single bus.

The different buses are arranged in a hierarchical fashion.

The top-level bus is the processor bus, which the PC's chipset uses to send information
to and from the CPU.

Some higher-level PC architectures (Pentium II and Pentium Pro, for example) use
a cache bus.

This is a dedicated bus used for accessing the system cache.

The next level in the bus hierarchy is the memory bus, which connects the memory
subsystem to the chipset and the processor.

However, it is worth noting that in some PCs the memory bus and the processor bus
are the same thing.

The local I/O bus is at the next level in the hierarchy.

This bus (for example, a VESA bus or a PCI bus) is used for connecting certain peripherals
to the memory, chipset, and processor.

Such peripherals would include video cards, disk storage devices, and high-speed
network interfaces.

Beneath the local I/O bus is the standard I/O bus.

This is used to connect slower peripherals, such as mouse devices or standard sound
cards, to the processor, chipset, and memory.

It is also important for backward compatibility with older devices.

In almost all PCs, this standard I/O bus is the PCI bus.

On a system that has multiple buses, circuitry must be provided by the chipset to
connect the buses and enable them to communicate with each other and with the CPU.

Coordination of multiple buses can therefore be quite a complex task for the chipset.

In such a situation, the PCI bus nearest the CPU is known as the primary bus, and
the other PCI bus is known as the secondary PCI bus.

The two buses are connected by a PCI-to-PCI bridge.

In the Intel model, the use of a secondary PCI bus and the PCI-to-PCI bridge allows
for a docking station, to which a portable PC, for example, could be connected.

Such a docking station can have its own set of peripheral devices, thus enhancing
the functionality of the PC.

There is no single way to configure buses in a PC.

Rather, there are several different methods, each one having its own advantages
and disadvantages.

The most important thing to consider is the needs of the PC user, and which combination
of bus technologies will best meet those needs.

Quiz

Basic Elecricity

Techonology

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