What is Southbridge?

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  • Written By: R. Kayne
  • Edited By: O. Wallace
  • Last Modified Date: 27 September 2019
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If you’re in the market for a motherboard you’ll likely come across much talk about chipsets. The chipset of a motherboard is so important that many people will chose a motherboard based on the chipset manufacturer they prefer. The chipset is made up of two main chips: the Northbridge and Southbridge chips, a central part of the mainboard’s architecture. A handful of some of the more popular chipset manufacturers include nVidia®, Intel®, AMD®, SiS®, VIA®, and ATI®.

There is no overriding standard for designing chipset architecture and competition drives innovation and change. In the basic model the Northbridge chip handles the faster communication needs of the computer. These include systems communication with the computer processing unit (CPU), video card slot, Random Access Memory (RAM), and the Southbridge chip. The Northbridge is also known as the Memory Controller Hub (MCH), or Integrated Memory Controller (IMC).

The Southbridge controls the slower I/O or in-and-out devices. These include all hard drive and expansion slots, USB, FireWire, RAID, audio codecs, real-time system clock, system power management, interrupt controller, direct memory access (DMA) controller, and nonvolatile BIOS memory. The Southbridge chip is sometimes referred to as the I/O Controller Hub (ICH), or Platform Controller Hub (PCH).


In legacy mainboard designs every different device the Southbridge now handles used to be controlled by a discreet chip on the motherboard. Combining these into one chip to rule them all saved real estate and manufacturing costs. The various linkages or data pathways between chips and components on the motherboard are referred to as buses. A motherboard with a faster bus speed will be quicker than a motherboard with a slower bus speed, all else being equal.

The chipset dictates what type of CPU and features the system will be able to support, and which features it will be missing. If you’ve ever tried to upgrade an older computer with new technology and were told your chipset doesn’t support it, it was the Northbridge and Southbridge chips being referenced. To help future-proof any new investment, it’s always best to buy a motherboard with a chipset that supports the newest breaking technology.

At least one current chipset design has integrated the Northbridge and Southbridge into a single chip. Some chipsets, including the aforementioned, are incorporating a graphics processing unit (GPU) for faster image processing. Previously, a GPU could only be had on a high-end graphics card, located on the card itself. Graphics cards that do not have a GPU rely on the CPU for processing. Incorporating a GPU in the chipset makes for faster graphics rendering, a real plus that should please gamers.


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