It is a collection of chips or circuits designed to work with a specific family of microprocessors and all chips work together to interface with peripheral devices for the CPU. It interfaces memory, expansion cards, and peripherals. Because it controls communications between the processor and devices, the chipset plays a crucial role in determining system performance.
Chipsets are usually given a name and model number by the original manufacturer. For example, if 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.
It also tells that a particular chipset has a certain set of features like, onboard video or audio of a certain type/brand. The functions of chipsets can be divided into two major functional groups, called Northbridge and Southbridge
The Northbridge subset of a motherboard’s chipset is the set of circuitry or chips that manages high-speed peripheral communications. It is responsible for communications with integrated video using AGP and PCIe. 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 front side 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).
It also manage the communications between the Southbridge chipset and the rest of PC. If motherboard has onboard video circuitry, that circuitry will be found in Northbridge chipset.
It is responsible for providing support to all remaining onboard peripherals (PS/2, Parallel, IDE, and so on), managing their communications with the rest of the computer and the resources given to them. Motherboards today have integrated PS/2, USB, Parallel, and Serial. Some other optional features handled by Southbridge include LAN, audio, infrared, and FireWire (IEEE 1394). It is also responsible for managing communications with the other expansion buses, such as PCI, USB, and legacy buses.