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 onboard control tasks.

A southbridge chipset handles functions such as USB, audio, the system BIOS, the ISA bus or the LPC bus, the low speed PCI/PCIe bus, the IOAPIC interrupt controller, the SATA storage, the historical PATA storage, and the NVMe storage.^[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). 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.

As of 2024, most personal computer devices no longer use a set of two chips, and instead have a single chip acting as the 'chipset', for example Intel's Z790 chipset.