Southbridge
From TPU Reference
Also: ICH (I/O Controller Hub)
The Southbridge is not directly connected to the CPU, but connected to the Northbridge.
Often the Northbridge / Southbridge combination is called Chipset, putting more focus on the selected Northbridge than the Southbridge. For example you hear people talking about "I have an i975X chipset on my motherboard". Northbridges can not work with all Southbridges. Depending on the manufacturer and platform, there are several Southbridges to choose from when using a certain Northbridge. For example the ATI RD580 Northbridge can be paired with the ATI SB400, ATI SB600, ULi M1575 and others.
In some cases Northbridge and Southbridge are combined into a single chip. This is done to reduce cost of lower end chipsets, taking away a bit of design flexibility.
The term Northbridge comes from the arrangement of the devices. If you look at the schematics like you would look at a map, the Northbridge and CPU are in the northern part of the map, the southbridge in the southern part.
Functions
Functions of Southbridges include:
- PCI-Express x1 bus
- PCI bus
- ISA bus
- SMBus
- DMA controller
- Interrupt controller
- IDE (SATA or PATA) controller
- LPC Bridge
- Real Time Clock
- Power management (APM and ACPI)
- Nonvolatile BIOS memory (flash)
- Ethernet
- USB
- Audio
- FireWire
