Southbridge
The southbridge is an IC (integrated circuit) on the motherboard responsible for the hard drive controller, I/O controller and integrated hardware. Integrated hardware can include the sound card and video card if on the motherboard, USB (universal serial bus), PCI, ISA (Industry Standard Architecture), IDE (integrated drive electronics), BIOS (basic input/output system), and Ethernet.
The southbridge gets its name for commonly being South of the PCI (peripheral component interconnect) bus. Below is a graphic illustration of the ASUS P5AD2-E motherboard with explanations of each of the major components including the southbridge. It is common for the northbridge and southbridge to have a heat sink. Also, the northbridge is usually slightly larger than the southbridge.
Although the southbridge handles most of the I/O devices, less prominent input/output devices, such as a serial port, keyboard, and non-USB mouse are handled by the SIO (super input/output).
Some newer chipsets are combining the Southbridge and Super I/O chips into a single chip and referring to this chip as the Super Southbridge chip. Some manufacturers such as NVIDIA and SiS have even combined the Northbridge, Southbridge, and Super I/O into a single chip.
New motherboards are replacing the northbridge and the southbridge with IHA (Intel Hub Architecture).
Chipset, Hardware terms, ICH, Motherboard, Motherboard terms, Northbridge, PIIX