from: click here
Northbridge is an Intel chipset that communicates with the computer processor and controls interaction with memory, the Peripheral Component Interconnect (PCI) bus, Level 2 cache, and all Accelerated Graphics Port (AGP) activities. Northbridge communicates with the processor using the frontside bus (FSB). Northbridge is one part of a two-part chipset called Northbridge/Southbridge. Southbridge handles the input/output (I/O) functions of the chipset.
The Intel Hub Architecture (IHA) has replaced the Northbridge/Southbridge chipset. The IHA chipset also has two parts: the Graphics and AGP Memory Controller Hub (GMCH) and the I/O Controller Hub (ICH). The IHA architecture is used in Intel's 800 series chipsets, which is the first chipset architecture to move away from the Northbridge/Southbridge design.
Sorry I don't know the practicalities of it all.