Chipsets

A typical motherboard chipset (click image for bigger image)

A chipset is a collection of chips or circuits that perform interface and peripheral functions for the
processor.

This collection of chips is usually the circuitry that provides interfaces for memory, expansion cards, and onboard peripherals and generally dictates how a motherboard will talk to the installed peripherals.

Chipsets are usually given a name and model number by the original manufacturer. For example, if you see that motherboard has a VIA KT7 chipset, you would know that the circuitry for controlling peripherals was designed by VIA and was given the designation KT7.

Typically, that would also mean that you would know that a particular chipset has a certain set of features (for example, onboard video of a certain type/brand, onboard audio of a particular
type, and so on).

Chipsets can be made up of one or several integrated circuit chips. Intel-based motherboards typically use two chips, whereas the SiS chipsets typically use one. To know for sure, you must check the manufacturer’s documentation.

The functions of chipsets can be divided into two major functional groups, called Northbridge and Southbridge.

Northbridge

The Northbridge subset of a motherboard’s chipset is the set of circuitry or chips that performs
one very important function: management of high-speed peripheral communications.

The Northbridge subset is responsible primarily for communications with integrated video using
AGP and PCIe, for instance, and processor-to-memory communications.

Therefore, it can be said that much of the true performance of a PC relies on the performance of the Northbridge chipset and the communications between it and the peripherals it controls.

The communications between the CPU and memory occur over what is known as the frontside bus (FSB), which is just a set of signal pathways between the CPU and main memory. The backside bus, on the other hand, is a set of signal pathways between the CPU and Level 2 cache
memory (if present).

The Northbridge chipsets also manage the communications between the Southbridge chipset (discussed next) and the rest of the computer.

Finally, if a motherboard has onboard video circuitry (especially if it needs direct access to main memory), that circuitry will be found within the Northbridge chipset.

Southbridge

The Southbridge chipset, as mentioned earlier, is responsible for providing support to the myriad onboard peripherals (PS/2, Parallel, IDE, and so on), managing their communications with the rest of the computer and the resources given to them.

Most motherboards today have integrated PS/2, USB, Parallel, and Serial. Some of the optional features handled by the Southbridge include LAN, audio, infrared, and FireWire
(IEEE 1394).

When first integrated, the quality of onboard audio was marginal at best, but the latest offerings (such as the AC97 audio chipset) rival Creative Labs in sound quality and number of features (even including Dolby Digital Theater Surround technology).

The Southbridge chipset is also responsible for managing communications with the other expansion buses, such as PCI, USB, and legacy buses.