The chipset are the set of microchips used on a Motherboard. Three companies make the vast majories of chipsets Intel, NVIDIA and AMD. In todays marketplace chipsets come in three configurations; Traditional, Modern and Post-Modern.
Traditional chipsets are the oldest of all the chipsets. These contain a northbridge and southbridge chip. The CPU is considered the northpole (closest to the northbridge) and the slowest devices connect to the southpole. The Southbridge does not require extra cooling (heat sink or fan) so is a good place to see the manufacturer of a chipset (eg Intel).
Northbridge = CPU to communicate with RAM and Video Card
Southbridge = CPU to communicate with Devices (eg hard drives)
Most motherboards support old technologies such as floppy drives or parallel ports, the support used to be by the southbridge. Now motherboards have a dedicated Super I/O to handle this as newer chipsets do not support these devices.
In 2003 AMD launched the Athlon 64 microprocessor. The Athlon 64 contains the memory controller on the CPU so the northbridge no longer needs to handle the communication with RAM. The Northbridge duties changed to dealing with the video card(s) and southbridge. Intel switched to the same configuration with their release of the Core i7 processor and the X58 Express chipset. Intel also changed the name of the northbridge to the I/O Hub.
In 2009 Intel’s P55 Express chipset, the CPU incorporates the memory controller and video interface meaning there is no need for a nothbridge at all. Intel don’t use the term southbridge for the remaining ‘southbridge’ chip but refer to it as the Platform Controller Hub (PCH). AMD also switched to this configuration with the launch of the Fusion platform.