Northbridge v/s Southbridge
Northbridge:
The Northbridge is one of the two chips in the core logic chipset on a PC motherboard, 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.

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.