What is Northbridge?

R. Kayne

The Northbridge and Southbridge chips comprise what is known as a chipset on modern computers. The chipset is responsible for facilitating communication between the computer processing unit (CPU) and the various components on the motherboard, acting as traffic cops and controllers. Since the Northbridge is working constantly, it can become very hot and in many cases it has its own heatsink. Other names for the chip include the Memory Controller Hub (MCH) and the Integrated Memory Controller (IMC).

The Northbridge chipset may have its own heatsink.
The Northbridge chipset may have its own heatsink.

This chip is located closest to the CPU and controls the fastest components on the motherboard: the CPU, video card slot, and random access memory (RAM). If the CPU cache is found on the motherboard, it also falls under the control of the Northbridge, as does the Southbridge chip. These components are all connected via pathways known as buses, making the bus speed of the computer an important specification in overall performance.

A CPU. The northbridge, part of a computer's chipset, helps the CPU to communicate with other motherboard components.
A CPU. The northbridge, part of a computer's chipset, helps the CPU to communicate with other motherboard components.

The Southbridge handles the slower traffic on the computer, or the I/O (in and out) devices. SATA and IDE hard drive and expansion slots, RAID, USB, FireWire®, direct access memory (DMA) controller, system clock, power management, interrupt controller, and audio codecs all fall under the control of the this chip. It is also referred to as the I/O Controller Hub (ICH) or Platform Controller Hub (PCH).

While people are used to thinking of the CPU as being the most important element on a motherboard, it’s actually the Northbridge that dictates which type of CPU and RAM can be used on the motherboard. Overclocking ability also depends on the chip. The Southbridge dictates which features the computer will have, and whether or not the newest technologies will be supported. Since only one or two Southbridge chips can be paired with a particular Northbridge chip, the entire system is essentially based around that one chip.

Due to the overriding influence of the chipset, many people choose their computer systems based on the chipset manufacturer that might develop a reputation for excelling in one area or another, usually in graphics support. There is no industry standard for chipset design, driving creative competition between the major manufacturers. Some current designs have incorporated both chips into a single die. Another trend is to include a graphics processing unit (GPU) in the chipset, which saves the CPU from having to process the great amounts of data required for high-definition rendering.

The Northbridge chipset dictates what type of CPU and RAM is compatible with a motherboard.
The Northbridge chipset dictates what type of CPU and RAM is compatible with a motherboard.

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Discussion Comments


@Kristee: What you're most likely hearing (fan wise) is probably the CPU Heatsink and Fan. Northbridge cooling devices can vary from just a minor heatsink -- to huge heatsink and fan -- to even water cooling. For the most part, I feel safe saying that most Northbridge chips rely on a simple heatsink alone (maybe this designs assumes that the host PC has adequate air flow to make this work without a dedicated fan on the Northbridge heatsink).

Fan wise, PC's have lots of fans. The most commonly noticeable fans are the CPU heatsink and fan, the power supply fan, and the case fans. I wonder if the fan you say you can hear is one of these instead.


@JackWhack – Overclocking means fixing your computer so that it can run at a faster speed than it was designed to run. I know that the Northbridge controls this, though I'm not exactly sure how. I think it's just because the Northbridge in the chipset is in charge of the more important things that affect the computer on a grand scale.

The Southbridge lets us use USB ports. So, when I stick my digital camera's memory card into a USB device on my computer, I am putting the Southbridge to work, as I understand it. I transfer photos from my camera to my computer often, so I really put it to work.


I know the bare minimum about computers. I can get on the internet and use a word processor, but that is about as far as my knowledge extends.

Can someone tell me an example of what the Northbridge does? For example, what does “overclocking” mean? Also, I would like to know something that the Southbridge does, so that I can compare the two.


@Kristee – A lot of times, Northbridge cooling is accomplished with a fan that runs between the fins of a heatsink. The heatsink itself can vary greatly in appearance, because there are so many kinds available. I've seen some that resemble the filters you put in your vacuum cleaner, while others look more like small beds of nails.

My dad is a computer whiz, and I've watched him take apart and reassemble computers before. Since he has worked on many different ones for clients, I've seen quite a few heatsinks.

There are some that don't even use a fan. They are made of material that conducts the heat away from the Northbridge so well that a fan just isn't necessary.


I always knew that some part of my computer would get really warm, but I didn't know it was called a Northbridge. I can hear a fan running inside there, and I guess it's operating to cool the inside down.

What does a Northbridge heatsink look like? Does it have fluid in it to cool it off, or does it draw the heat toward some sort of coolant?

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