Northbridge
This refers to the major bus controller circuitry, like the memory, cache, and PCI controllers.
The north bridge may have more than one discrete chip. The entire chipset is named after
the numbers on the primary or largest north bridge chip.
Southbridge
This refers to the peripheral and non-essential controllers, like EIDE and serial port controllers.
The south bridge usually has only one discrete chip, and has the benefit of being interchangeable
on many different chipsets (e.g. SiS 5513 or Intel PIIX).
