Southbridge (computing)

In computing, a southbridge is a component of a traditional two-part chipset architecture on motherboards, historically used in personal computers. It works alongside the northbridge to manage communications between the central processing unit (CPU) and lower-speed peripheral interfaces. The northbridge typically handled high-speed connections such as RAM and GPU interfaces, while the southbridge managed lower-speed functions.

The southbridge controls a range of input/output (I/O) functions, including USB, audio, firmware (e.g., BIOS or UEFI), storage interfaces such as SATA, NVMe, and legacy PATA, as well as buses like PCI, LPC, and SPI.^[1][2]

Southbridge and northbridge components were often designed to work in pairs, though there was no universal standard for interoperability.^[3] In the 1990s and early 2000s, they commonly communicated via the PCI bus; more recent chipsets use Direct Media Interface (Intel) or PCI Express (AMD).

Intel referred to its southbridge as the I/O Controller Hub (ICH), later replaced by the Platform Controller Hub (PCH), which connected directly to the CPU in later architectures. Since the mid-2010s, the traditional two-chip design has largely been replaced by single-chip platforms or system-on-chip (SoC) solutions that integrate southbridge functions into a single chipset or the CPU itself.