What is a North Bridge?

A North Bridge is the Intel term for the main portion of the motherboard chipset which combines the interface between the processor and an assortment of other relatively fast I/O centric peripheral devices such as controllers for the cache, main memory, the AGP bus, and the PCI bus(es).

Together, the North Bridge, the South Bridge, and perhaps some additional glue logic make up what is known as the motherboard's chipset.

Many modern chipsets also do a lot of on-the-fly optimizations with processor memory read/write operations and I/O bus communications.