northbridge or host bridge is one of two chips in the core logic chipset architecture on the PC motherboard, the other is the southbridge. Unlike the southbridge, the northbridge connects directly to the CPU through a front-side bus (FSB) and is thus responsible for tasks that require the highest performance. Northbridge is usually paired with the southbridge, also known as the I/O controlling hub. In the system where they are included, the two chips manage communications between the CPU and other parts of the motherboard, and are the core logic chipsets of the PC motherboard.
On older Intel-based PCs, the northbridge is also named hub memory controller hub ( MCH ) or graphics and memory controller > ( GMCH ) if equipped with integrated graph. More and more of these functions become integrated into the CPU chip itself, starting with the memory and graphics controller. For Intel Sandy Bridge processors and the AMD Accelerated Processing Unit introduced in 2011, all northbridge functions are on the CPU, while AMD FX CPUs still require an external northbridge and a southbridge chip.
Separating the various functions into CPU, northbridge, and southbridge chips is due to the difficulty of integrating all the components into one chip. In some cases, the northbridge and southbridge functions have been combined into one die when the design complexity and fabrication process allow it; for example, Nvidia GeForce 320M on MacBook Air 2010 is a northbridge/southbridge/GPU combo chip.
As CPU speed increases over time, bottlenecks eventually arise between the processor and the motherboard, due to limitations caused by data transmission between the CPU and its support chipsets. Thus, starting with AMD Athlon64 series CPUs (based on Opteron), a new architecture is used in which some north- and southbridge chip functions are transferred to the CPU. The modern Intel Core processor has an integrated northbridge on the CPU die, where it is known as an uncore or a system agent.
Video Northbridge (computing)
Overview
Northbridge typically handles communication between CPUs, in some cases RAM, and PCI Express (or AGP) video cards, and southbridge. Some northbridges also contain an integrated video controller, also known as Graphics and Memory Controller Hub (GMCH) in Intel systems. Because different processors and RAMs require different signals, the given northbridge will typically work with only one or two CPU classes and generally only one type of RAM.
There are several chipsets that support two types of RAM (this is generally available when there is a shift to the new standard). For example, the northbridge of 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 clock speeds greater than 1.3 GHz and use DDR SDRAM, and the Intel i915g chipset works only with Intel Pentium 4 and Celeron but can use DDR or DDR2.
Maps Northbridge (computing)
Etymology
This name comes from drawing the architecture in map mode. The CPU will be at the top of the map that is proportional to the north on the most common geographical map. The CPU will connect to the chipset via a fast bridge (northbridge) located to the north of other system devices as drawn. The northbridge will then connect to the entire chipset via a slow bridge (southbridge) located to the south of other system devices as they are drawn.
Overclocking
Northbridge plays an important part in how far a computer can be overclocked, because its frequency is often used as a basis for the CPU to set its own operating frequency. These chips usually become hotter as the processor speed becomes faster, requiring more cooling. There is a limit for CPU overclocking, since digital circuits are limited by physical factors such as slew rate of operational amplifiers and propagation delays, which increases with (among other factors) operating temperatures; consequently most overclocking applications have software-imposed restrictions on the multiplier and external clock settings.
Evolution
The overall trend in processor design is to integrate more functions into fewer components, which lower overall motherboard costs and improve performance. The memory controller, which handles communications between the CPU and RAM, is transferred to AMD processors by AMD64 processors starting with their AMD64 processors and by Intel with their Nehalem processors. One of the advantages of having an integrated memory controller on CPU die is to reduce latency from CPU to memory.
Another example of this kind of change is nForce3 nvidia for the AMD64 system. It combines all the features of a normal southbridge with an Accelerated Graphics Port (AGP) port and connects directly to the CPU. On board nForce4 is marketed as media communication processor (MCP).
The AMD Accelerated Processing Unit processor features full integration of northbridge functionality to the CPU chip, along with processor cores, memory controllers and graphics processing units (GPUs). This is an evolution of AMD64, because the integrated memory controller on the CPU dies in AMD64.
The northbridge was replaced by a system agent introduced by Sandy Bridge microarchitecture in 2011, which essentially handles all previous Northbridge functions. Intel's Sandy Bridge processors feature full integration of northbridge functionality to CPU chips, along with processor cores, memory controllers and graphics processing units (GPUs). This is a further evolution of the Westmere architecture, which also features CPUs and GPUs in the same package.
See also
- Southbridge
- Chipset
- Intel Management Engine (ME)
References
Source of the article : Wikipedia
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