Motherboards and Buses - Upgrading and Repairing PCs - page 217

Traditional North/South Bridge Architecture
Most of Intel's earlier chipsets as well as earlier non-Intel chipsets, use a multitiered ar-
chitecture incorporating what are referred to as North and South Bridge components, as
well as a Super I/O chip:
• The North Bridge —So named because it is the connection between the high-speed
processor bus and the slower AGP and Peripheral Component Interconnect (PCI)
buses.TheNorthBridgeiswhatthechipsetisnamedafter,meaningthat,forexample,
what we call the 440BX chipset is derived from the fact that the actual North Bridge
chip part number for that set is 82443BX.
• The South Bridge —So named because it is the bridge between the PCI bus (66/
33MHz) and the even slower ISA bus (8MHz).
• The Super I/O chip —It's a separate chip attached to the ISA bus that is not really
considered part of the chipset and often comes from a third party, such as National
Semiconductor or Standard MicroSystems Corp. (SMSC). The Super I/O chip in-
cluded commonly used peripheral items combined into a single chip. Note that more
recentSouthBridgechipsincludeSuperI/Ofunctions(suchchipsareknownasSuper-
South Bridge chips), so that the most recent motherboards based on a North/South
Bridge architecture no longer include a separate Super I/O chip.
See “ Super I/O Chips ,” p. 214 (this chapter).
Figure4.20 showsatypicalAMDSocketAmotherboardusingNorth/SouthBridgearchi-
tecture with the locations of all chips and components.
Figure 4.20 A typical Socket A (AMD Athlon/Duron) motherboard showing component locations.