Northbridge v/s Southbridge

Northbridge:

The Northbridge is one of the two chips in the core logic chipset on a PCmotherboard, the other being the Southbridge. In Intel chipset systems it is named memory controller hub (MCH) or integrated memory controller (IMCH) if equipped with an integrated VGA.

Separating the chipset into the Northbridge and Southbridge is common, although there are rare instances where these two chips have been combined onto one die when design complexity and fabrication processes permit it.

The Northbridge typically handles communications among the CPU, RAM, BIOS ROM, and PCI Express (or AGP) video cards, and the Southbridge.[1][2] Some north bridges also contain integrated video controllers, also known as a Graphics and Memory Controller Hub (GMCH) in Intel systems. Because different processors and RAM require different signaling, a Northbridge will typically work with only one or two classes of CPUs and generally only one type of RAM.

There are a few chipsets that support two types of RAM (generally these are available when there is a shift to a new standard). For example, the Northbridge from the Nvidia nForce2 chipset will only work with Socket A processors combined with DDR SDRAM, the Intel i875 chipset will only work with systems using Pentium 4 processors or Celeron processors that have a clock speed greater than 1.3 GHz and utilize DDR SDRAM, and the Intel i915g chipset only works with the Intel Pentium 4 and the Celeron, but it can use DDR or DDR2 memory.

Southbridge:

The Southbridge is one of the two chips in the core logic chipset on a PCmotherboard, the other being the Northbridge. The Southbridge typically implements the "slower" capabilities of the motherboard in Northbridge /Southbridge chipset computer architecture. In Intel chipset systems theSouthbridge is named Input/Output 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.

Difference between Southbridge and Northbridge:

North and south bridge refer to the data channels to the CPU, memory and Hard disk data goes to CPU using the Northbridge. And the mouse, keyboard, CD ROM external data flows to the CPU using the Southbridge.

The Northbridge is the portion of the chipset HUB that connects faster I/O buses (for example, an AGP bus) to the system bus. Northbridge SI also bigger looking then the Southbridge chip. The Southbridge is the HUB that connects to slower I/O buses (for example, An ISA bus) to the system bus.

The Northbridge and the Southbridge are known as the chipset on themotherboard. These set of chips collectively control the memory cache, external bus, and some peripherals. There is a fast end of the hub, and there is a slow end of the hub. The fast end of the hub is the Northbridge, containing the graphics and memory controller connecting to the system bus. The slower end of the hub is the Southbridge, containing the I/O controller hub.

source : http://computer-help-tips.blogspot.co.id/2011/04/northbridge-vs-southbridge.html