The Northbridge is directly connected to the CPU and handles the data flows between CPU, BIOS, RAM, the video card and the Southbridge chip. For communication with each of these elements a protocol, a so-called 'bus', is used.
The Northbridge manages:
- the Front-side Bus (FSB) between Northbridge and CPU.
- the Chipset Interconnect bus between Northbridge and Southbridge.
- the PCI-express (or AGP) bus of the video card.
- the Memory Bus between Northbridge and system memory (RAM)
Some Northbridge chips also have an integrated graphics processor, which makes a dedicated video card less necessary (depending on the performance required).
The performance measure for each of these buses is the maximum amount of data that can be moved per unit of time. This depends on the clock speed, the data-width and the latency (or 'access' time). The influence of the latter depends very much on the specific micro-architecture of the software and is difficult to quantify in general terms. The data-width used to be easy to define as 32 bit for a typical Pentium (like) processor. However, with the appearance of parallel processing, double data channels (2 x 32 bit), etc. things have become more complicated.
For all these reasons manufacturers are referring less and less to clock speed and data-width, but are simply referring to the performance in GB/s (gigabytes per second). The power requirement -and therefore the heat dissipation- of the Northbridge is in the same league as the CPUs that were introduced on the market one year ago. Specific coolers exist for the Northbridge chip, especially for use with overclocked PCs. The energy consumption (power x time) of the chipset (Northbridge+Southbridge) may be higher than that of the CPU in typical office use (e.g. BatteryMark tests).
Courtesy of the French Energy Agency ADEME, Future Electronics project. Expanded by VHK.