The chipset is the "glue" that connects the microprocessor to the rest of the motherboard and therefore to the rest of the computer. On older PCs, it consists of two basic parts — the northbridge and the southbridge. All of the various components of the computer communicate with the CPU through the chipset.
The northbridge connects directly to the processor via the front side bus (FSB). A memory controller located on the northbridge gives the CPU fast access to the memory. The northbridge also connects to the AGP or PCI Express bus and to the memory itself.
The southbridge is slower than the northbridge, and information from the CPU must go through the northbridge before reaching the southbridge. Other buses connect the southbridge to the PCI bus, the USB ports and the IDE or SATA hard disk connections.
In the early 2000s, Intel processors began using the Intel Hub Architecture, or IHA. It may also be referred to as the Accelerated Hub Architecture (AHA). The newer architecture uses its own buses, in the process dropping PCI entirely. IHA chips do not have a northbridge or southbridge. Instead, they have a Graphics and AGP Memory Controller Hub, or GMCH, and an I/O (input/output) Controller Hub, or ICH.
The GMCH performs a similar role to the northbridge, working with memory and graphics. The ICH takes over the jobs of the southbridge.
Chipset selection and CPU selection go hand in hand because manufacturers optimize chipsets to work with specific CPUs. The chipset is an integrated part of the motherboard, so it cannot be removed or upgraded. This means that not only must the motherboard's socket fit the CPU, the motherboard's chipset must work optimally with the CPU.
Next, we'll look at buses, which, like the chipset, carry information from place to place.