Southbridge (computing)

The southbridge is one of the two chips in the core logic chipset on older personal computer (PC) motherboards, the other being the northbridge. As of 2023, 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.

The southbridge typically implemented the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In systems with

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.

Current status

Due to the push for

A southbridge chipset handled many of a computer's I/O 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.[5]^[6] Different combinations of Southbridge and Northbridge chips are possible,^[7] but these two kinds of chips must be designed to work together;^[8][9] 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).

Etymology

The name is derived from representing the architecture in the fashion of a map and was first described as such with the introduction of the

The northbridge extends to the north of the PCI bus backbone in support of CPU, memory/cache, and other performance-critical capabilities. Likewise the southbridge extends to the south of the PCI bus backbone and bridges to less performance-critical I/O capabilities such as the disk interface, audio, etc.

The CPU is located at the top of the map at due north. The CPU is connected to the chipset via a fast bridge (the northbridge) located north of other system devices as drawn. The northbridge is connected to the rest of the chipset via a slow bridge (the southbridge) located south of other system devices as drawn.

Although the current PC platform architecture has replaced the PCI bus backbone with faster I/O backbones, the bridge naming convention remains.

Functionality

The functionality found in a contemporary southbridge includes:^[9][6]

• PCI bus. A south bridge may also include support for PCI-X
  .
• Low speed PCI Express (PCIe) interfaces usually for Ethernet and NVMe.
• ISA bus or LPC bridge. ISA slots are no longer provided on more recent motherboards. The LPC bridge provides a data and control path to the super I/O (the normal attachment for the PS/2 keyboard and mouse, parallel port, serial port, IR port, and floppy controller).
• SPI bus. The SPI bus is a simple serial bus mostly used for firmware (e.g., BIOS/UEFI) flash storage access.
• SMBus
  controller.
• main memory
  without needing help from the CPU.
• I/O APIC
  .
• SSDs
  .
• Real-time clock.
• Programmable interval timer.
• High Precision Event Timer.
• ACPI controller or APM
  controller.
• non-volatile
  storage area for BIOS configuration data.
• Intel HD Audio or AC'97
  sound interface.
• USB interfaces.

Optionally, a southbridge also includes support (onboard discrete chip or southbridge-integrated) for Ethernet, Wi-Fi, RAID, Thunderbolt, and Out-of-band management.

See also

• Memory controller
• Northbridge (computing)

References

External links

• "Motherboards & Core-Logic Chipsets: The Deep Stuff > What the North Bridge and South Bridge Do". InformIT. Retrieved November 18, 2010.