*Circuitry that ‘glues’ CPU, memory, buses & interfaces together.
Made by Intel, VIA, SIS, ALI
* Commonly consists of 2 chips, referred to as ‘Northbridge’ and ‘Southbridge’.
* Motherboard is designed around chipset and CPU.

The old way of doing chipsets has two components, the northbridge and the southbridge. The northbridge communicates with the CPU over the Front Side Bus (FSB) and acts as the controller for memory, AGP and PCI. The type of FSB, memory and AGP varies from northbridge to northbridge. Some northbridges integrate video as well.

The southbridge takes care of most basic forms of I/O, such as USB, serial ports, audio, IDE and more. What I/O is controlled depends on the specific southbridge. The southbridge sits on the northbridge's PCI bus, which is usually a 32-bit, 33MHz bus capable of providing 133MBps of bandwidth. Intel's 440BX chipset and all current VIA and AMD PC chipsets use this type of northbridge/southbridge architecture.

<a href="http://www.sharkyextreme.com/hardware/guides/intel_i815_chipset/2.shtml.">http://www.sharkyextreme.com/hardware/guides/intel_i815_chipset/2.shtml.</a