Southbridge (computing)

The southbridge is one of the two chips in the core logic chipset on a personal computer (PC) motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In systems with Intel chipsets, the southbridge is named I/O Controller Hub (ICH), while AMD has named its southbridge Fusion Controller Hub (FCH) since the introduction of its Fusion APUs.

The southbridge can usually be distinguished from the northbridge by not being directly connected to the CPU. Rather, the northbridge ties the southbridge to the CPU. Through the use of controller integrated channel circuitry, the northbridge can directly link signals from the I/O units to the CPU for data control and access.

Due to the push for system-on-a-chip (SoC) processors, modern devices increasingly have the northbridge integrated into the CPU die itself; examples are Intel's Sandy Bridge and AMD's Fusion processors, both released in 2011. The southbridge became redundant and it was replaced by the Platform Controller Hub (PCH) architecture introduced with the Intel 5 Series chipset in 2008. All southbridge features and remaining I/O functions are managed by the PCH which is directly connected to the CPU via the Direct Media Interface (DMI).

A southbridge chipset handles all of a computer's I/O functions, such as USB, audio, serial, the system BIOS, the ISA bus, the interrupt controller and the IDE channels. Different combinations of Southbridge and Northbridge chips are possible, but these two kinds of chips must be designed to work together; there is no industry-wide standard for interoperability between different core logic chipset designs. Traditionally, the interface between a northbridge and southbridge was the PCI bus. The main bridging interfaces used now are DMI (Intel) and UMI (AMD).

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