NORTHBRIDGE

Northbridge is an Intel chipset that communicates with the computer processor and controls interaction with memory, the Peripheral Component Interconnect (PCI) bus, Level 2 cache, and all Accelerated Graphics Port (AGP) activities. Northbridge communicates with the processor using the frontside bus (FSB). Northbridge is one part of a two-part chipset called Northbridge/Southbridge. Southbridge handles the input/output (I/O) functions of the chipset.

The Intel Hub Architecture (IHA) has replaced the Northbridge/Southbridge chipset. The IHA chipset also has two parts: the Graphics and AGP Memory Controller Hub (GMCH) and the I/O Controller Hub (ICH). The IHA architecture is used in Intel's 800 series chipsets, which is the first chipset architecture to move away from the Northbridge/Southbridge design.

Overview

The northbridge typically handles communications between the CPU, RAM, AGP or PCI Express, and the southbridge. Some northbridges also contain integrated video controllers, which are also known as a Graphics and Memory Controller Hub (GMCH) in Intel systems. Because different processors and RAM require different signalling, 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.