The high-speed part of a common chipset architecture in a computer. The Northbridge is the controller that interconnects the CPU to memory via the frontside bus (FSB). It also connects peripherals via high-speed channels such as PCI Express. The Northbridge may include a display controller, obviating the need for a separate graphics card.
The Southbridge controller handles the remaining I/O, including the PCI bus, parallel and Serial ATA drives (IDE), USB, FireWire, serial and parallel ports and audio ports. Earlier chipsets supported the ISA bus in the Southbridge. Starting with Intel's 8xx chipsets, Northbridge and Southbridge were changed to Memory Controller and I/O Controller (see Intel Hub Architecture
Northbridge Connects CPU to:
PCI Express (PCIe)
Southbridge Connects CPU to:
The Northbridge part of the chipset controls the high-speed channels, while the Southbridge controls the lower speed devices.