Southbridge (computing)

On older personal computer motherboards, the southbridge is one of the two chips in the core logic chipset, handling many of a computer's input/output functions. The other component of the chipset is the northbridge, which generally handles high speed onboard communications.

A southbridge chipset handles functions such as USB, audio, the system firmware, the lower speed PCI/PCIe buses, the IOAPIC interrupt controller, the SATA storage, the historical PATA storage, the NVMe storage, and low speed buses such as ISA, LPC, SPI, and/or eSPI.^[1][2] Different combinations of southbridge and northbridge chips are possible,^[3] but these two kinds of chips are designed to work together.^{[citation needed]} There is no industry-wide standard for interoperability between different core logic chipset designs. In the 1990s and early 2000s, the interface between a northbridge and southbridge was the PCI bus. As of 2023, the main bridging interfaces used are Direct Media Interface (Intel) and PCI Express (AMD).

The southbridge typically implements the slower capabilities of the motherboard in a northbridge-southbridge chipset computer architecture. In systems with Intel chipsets, the southbridge has been named I/O Controller Hub (ICH) and later replaced by Platform Controller Hub chipsets. In older Intel/AMD architectures the southbridge is usually linked to the northbridge, which in turn connected to the CPU. Circa 2004 and onward Intel architectures started to link southbridge directly to the CPU (e.g. via Direct Media Interface). Through the use of controller-integrated channel circuitry, the northbridge (or CPU itself) can directly link signals from the I/O units to the CPU for data control and access.

As of 2024, most personal computer devices based on Intel or AMD architectures no longer use a set of two chips, and instead have a single chip acting as the 'chipset', for example Intel's Z790 chipset, and a central processing unit.