Functions of North Bridge

After CPU North Bridge is the core chipset on the computer motherboard that controls data communication between CPU and Motherboard. It runs at full processor speed. It mainly works as Memory controller and System Controller. It incorporates interface between Processor and rest of motherboard components.

Chipset is actually numbered according to the number of North Bridge. Nvidia GeForce 320M is a Northbridge /Southbridge fabrication in a single chip. Following are some major functions that are performed by the North Bridge:

Processor Support: Chipset is the major decider on the motherboard that decides which processor is supported, of what speed and how many processors are supported? Following areas are covered by North Bridge under this:

CPU Interface Socket Type: North Bridge is interfaced with the processor through host processor bus and CPU socket. No. of processor sockets are available in the market for this purpose such as Socket 7,Socket -1, Socket A etc. This socket number is decider that which particular Processor class is supported on that motherboard.

Max. Speed of Processor: North Bridge works as speed controller for CPU. It Consists of Cache and main memory controller. North Bridge provides necessary interface with FSB (Front Side Bus) and PCI –Southbridge. Processor speed is dependent on FSB speed and clock multiplier.

Multiple Processor Support: Northbridge Provides the feature of using 2 or more processors on the same motherboard. It Controls both processors so that they do not interfere with each other and maximum efficiency can be obtained by sharing load.

L2 Cache Support: North Bridge contains the L2 (Level 2) Cache control circuitry. Following Functions are covered by this circuitry:

L2 Cache Size: Level2 Cache size is decided by the North Bridge. It may be 256 KB, 512KB or 3 MB. It is actually a buffer that contains recently accessed data by the processor that works at greater speed than main memory and is used to improve performance.

L2 Cache Type: Three types of L2 caches are used namely Asynchronous, Synchronous Burst and Pipeline Burst. All uses different circuitry for its interface hence it’s important to know that whether it is supported with North bridge or not.

L2 Cache Write Policy:  Two types of write policies are used i.e. Write-Through, Write-Back. In write-Through memory writes are sent to main memory and cache as soon as the processor sends out information. But in case of Write-Back processor writes information to cache which is later written to main memory at appropriate time.

System Cacheable Memory: Memory Controller Circuitry, Chipset Cache and Tag RAM on the motherboard are major decider of memory that a system can cache.

Main Memory Support: Main memory is connected to the Processor by means of North Bridge. Hence it is decided by the North Bridge that what type of main memory and of what speed is supported. Memory read write operations are controlled by chipset. Hence Chipset decides which memory will be more compatible such as FPM, EDO, SDRAM or DDR RAM etc.

Max. Main Memory Size:  Northbridge is the major decider of maximum memory that a processor can support. It performs the function of translating Processor’s requests for instructions and data into addresses.

AGP Support: North Bridge provides an interface between AGP bus and Processor bus. Due to this functionality of North Bridge it sometimes also referred to as PAC (PCI/AGP Controller).