The southbridge is one of the two chips in the core logic chipset

Chipset

A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...

 on a personal computer

Personal computer

A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

 (PC) motherboard

Motherboard

In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...

, the other being the northbridge

Northbridge (computing)

The northbridge has historically been one of the two chips in the core logic chipset on a PC motherboard, the other being the southbridge. Increasingly these functions have migrated to the CPU chip itself, beginning with memory and graphics controllers. For Intel Sandy Bridge and AMD Fusion...

. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset

Chipset

A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...

 computer architecture. In Intel chipset systems, the southbridge is named Input/Output Controller Hub (ICH)

I/O Controller Hub

I/O Controller Hub , also known as Intel 82801, is an Intel southbridge on motherboards with Intel chipsets . As with any other southbridge, the ICH is used to connect and control peripheral devices.- ICH :...

. AMD, beginning with its Fusion

AMD Fusion

AMD Fusion is the marketing name for a series of APUs by AMD. There are two flavors of Fusion currently available, one with its CPU logic based on the Bobcat core and the other its CPU logic based on the 10h core. In both cases the GPU logic is HD6xxx, which itself is based on the mobile variant of...

 APUs, has given the label FCH, or Fusion Controller Hub, to its southbridge.

The southbridge can usually be distinguished from the northbridge by not being directly connected to the CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

.