What are Northbridge and Southbridge and what can they do for me?
Northbridge and Southbridge are chip sets that handle communications functions on most PC type motherboards. The Northbridge is a controller chip that handles interaction between the processor, memory, the Level 2 cache, the PCI bus, and the Accelerated Graphics Port (AGP). The components that benefit most from fast communication with the processor, in other words. It uses the fast Front Side Bus (FSB) to link the various components. The Southbridge handles more basic, slower, forms of I/O, such as serial ports, USB ports, and IDE. The Southbridge is attached to the Northbridge's PCI bus.
The Northbridge-Southbridge chips enormously speed up modern computers. They are used by VIA and AMD chipsets as well as some Intel chip sets, so they are what you will find on almost all current computers. The Northbridge-Southbridge combination represents a basic minimum architecture for a modern computer and you'd be hard put to find one that doesn't use them.
The exceptions are computers that use Intel's new Intel Hub Architecture (IHA). Like Northbridge-Southbridge, IHA uses two chips, called hub controllers, to handle communications between the processor and the other system components. However, the Graphics and AGP Memory Hub (GMCH), the equivalent of the Northbridge, doesn't handle the PCI bus. That is now handled by the I/O Controller Hub (ICH), which sits on a bus and is twice as fast as the Southbridge's bus. More importantly, the IHA bus can detect different data types as they move over the bus and optimize bus performance for the kinds of data being handled.