Hardware Reference
In-Depth Information
Traditional North/South Bridge Architecture
Most of Intel's earlier chipsets as well as earlier non-Intel chipsets use a multitiered architecture
incorporating what are referred to as North and South Bridge components, as well as a Super I/O
chip:
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. The North Bridge is
what the chipset is named after, meaning that, for example, what we call the 440BX chipset is
derived from the fact that the actual North Bridge chip part number for that set is 82443BX.
South Bridge —So named because it is the bridge between the PCI bus (66/33MHz) and the
even slower ISA bus (8MHz).
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 came from a third party, such as National Semiconductor or Standard
MicroSystems Corp. (SMSC). The Super I/O chip included commonly used peripheral items
combined into a single chip. Note that more recent South Bridge chips include Super I/O
functions (such chips are known as Super-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. 228 .
Figure 4.20 shows a typical AMD Socket A motherboard using North/South Bridge architecture with
the locations of all chips and components.
Figure 4.20. A typical Socket A (AMD Athlon/Duron) motherboard showing component
locations.
The North Bridge is sometimes referred to as the PAC (PCI/AGP Controller). It is essentially the
 
 
 
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