In Northbridge/Southbridge chipset architecture designs, the Northbridge is the chip or chips that connect a CPU to memory, the PCI bus, Level 2 cache and AGP activities. The Northbridge chips communicate with the CPU through the FSB.
The Northbridge chip is one of two chips that control the functions of the chipset. The other is the Southbridge. The Northbridge can consist of more than one discrete chip while the Southbridge is typically only one discrete chip.