Northbridge (computing)
Encyclopedia
The northbridge has historically been one of the two chips in the core logic chipset
on a PC motherboard, the other being the southbridge
. Increasingly these functions have migrated to the CPU chip itself, beginning with memory and graphics controllers. For Intel Sandy Bridge
and AMD Fusion
processors introduced in 2011, all of the functions of the northbridge reside on the CPU. When a separate northbridge is employed in older Intel systems it is named memory controller hub (MCH) or integrated memory controller hub (IMCH) if equipped with an integrated VGA.
Separating the different functions into the CPU, northbridge, and southbridge chips is due to the difficulty of integrating all components onto a single chip. In some instances the northbridge and southbridge functions were combined onto one die
when design complexity and fabrication processes permitted it, for example the Nvidia
GeForce
320M in the 2009/2010 Macbook Air is a northbridge/southbridge/GPU combo chip.
, in some cases RAM
, and PCI Express
(or AGP
) video cards, and the southbridge
. Some northbridges also contain integrated video controllers, also known as a Graphics and Memory Controller Hub (GMCH) in Intel systems. Because different processors and RAM require different signaling, a given 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.
via a fast bridge (the northbridge) located north of other system devices as drawn. The northbridge would then be connected to the rest of the chipset via a slow bridge (the southbridge) located south of other system devices as drawn.
, which handles communication between the CPU and RAM, were moved onto the processor die
by AMD beginning with their AMD64 processors and by Intel with their Nehalem processors. One of the advantages of having the memory controller integrated on the CPU die is to reduce latency from the CPU-to-Memory so the CPU can control the memory directly.
Another example of this kind of change is Nvidia
's nForce3
chipset for AMD64 systems that is a single chip. It combines all of the features of a normal southbridge
with an AGP
port and connects directly to the CPU. On nForce4
boards they consider this to be an MCP (Media Communications Processor).
Intel's "Sandy Bridge" processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller and graphics processing unit (GPU). This was a further evolution of the Westmere architecture, which also featured a CPU and GPU in the same package.
AMD Fusion
processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller and graphics processing unit (GPU). This was an evolution of the AMD64, since the memory controller was integrated on the CPU die in the AMD64.
, as its frequency is commonly used as a baseline for the CPU to establish its own operating frequency. This chip typically gets hotter as processor speed becomes faster, requiring more cooling. There is a limit to CPU overclocking
, as digital circuit
s are limited by physical factors such as propagation delay
which increases with (among other factors) operating temperature
; consequently most overclocking applications have software-imposed limits on the multiplier
and external clock setting. See Overclocking
Chipset
A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...
on a PC motherboard, the other being the southbridge
Southbridge (computing)
The southbridge is one of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In Intel chipset...
. Increasingly these functions have migrated to the CPU chip itself, beginning with memory and graphics controllers. For Intel Sandy Bridge
Sandy Bridge
Sandy Bridge is the codename for a microarchitecture developed by Intel beginning in 2005 for central processing units in computers to replace the Nehalem microarchitecture...
and AMD Fusion
AMD Fusion
AMD Fusion is the marketing name for a series of APUs by AMD. There are two flavors of Fusion currently available, one with its CPU logic based on the Bobcat core and the other its CPU logic based on the 10h core. In both cases the GPU logic is HD6xxx, which itself is based on the mobile variant of...
processors introduced in 2011, all of the functions of the northbridge reside on the CPU. When a separate northbridge is employed in older Intel systems it is named memory controller hub (MCH) or integrated memory controller hub (IMCH) if equipped with an integrated VGA.
Separating the different functions into the CPU, northbridge, and southbridge chips is due to the difficulty of integrating all components onto a single chip. In some instances the northbridge and southbridge functions were combined onto one die
Die (integrated circuit)
A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon or other semiconductor through processes such as...
when design complexity and fabrication processes permitted it, for example the Nvidia
NVIDIA
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...
GeForce
GeForce
GeForce is a brand of graphics processing units designed by Nvidia. , there have been eleven iterations of the design. The first GeForce products were discrete GPUs designed for use on add-on graphics boards, intended for the high-margin PC gaming market...
320M in the 2009/2010 Macbook Air is a northbridge/southbridge/GPU combo chip.
Overview
The northbridge typically handles communications among the CPUCentral processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
, in some cases RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
, and PCI Express
PCI Express
PCI Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP bus standards...
(or AGP
Accelerated Graphics Port
The Accelerated Graphics Port is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics. Since 2004 AGP has been progressively phased out in favor of PCI Express...
) video cards, and the southbridge
Southbridge (computing)
The southbridge is one of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In Intel chipset...
. Some northbridges also contain integrated video controllers, also known as a Graphics and Memory Controller Hub (GMCH) in Intel systems. Because different processors and RAM require different signaling, a given 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
NVIDIA
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...
nForce2
NForce2
The nForce2 chipset was released by Nvidia in July 2002 as a refresh to the original nForce product offering. The nForce2 chipset was a platform for motherboards supporting AMD's Socket A CPUs along with DDR SDRAM...
chipset will only work with Socket A
Socket A
Socket A is the CPU socket used for AMD processors ranging from the Athlon Thunderbird to the Athlon XP/MP 3200+, and AMD budget processors including the Duron and Sempron. Socket A also supports AMD Geode NX embedded processors...
processors combined with DDR SDRAM
DDR SDRAM
Double data rate synchronous dynamic random access memory is a class of memory integrated circuits used in computers. DDR SDRAM has been superseded by DDR2 SDRAM and DDR3 SDRAM, neither of which are either forward or backward compatible with DDR SDRAM, meaning that DDR2 or DDR3 memory modules...
, the Intel i875 chipset will only work with systems using Pentium 4
Pentium 4
Pentium 4 was a line of single-core desktop and laptop central processing units , introduced by Intel on November 20, 2000 and shipped through August 8, 2008. They had a 7th-generation x86 microarchitecture, called NetBurst, which was the company's first all-new design since the introduction of the...
processors or Celeron
Celeron
Celeron is a brand name given by Intel Corp. to a number of different x86 computer microprocessor models targeted at budget personal computers....
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
DDR2 SDRAM
DDR2 SDRAM is a double data rate synchronous dynamic random-access memory interface. It supersedes the original DDR SDRAM specification and has itself been superseded by DDR3 SDRAM...
memory.
Etymology
The name is derived from drawing the architecture in the fashion of a map. The CPU would be at the top of the map comparable to due north on most general purpose geographical maps. The CPU would be connected to the chipsetChipset
A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...
via a fast bridge (the northbridge) located north of other system devices as drawn. The northbridge would then be connected to the rest of the chipset via a slow bridge (the southbridge) located south of other system devices as drawn.
Recent developments
The overall trend in processor design has been to integrate more functions onto the chip which decreases overall motherboard cost and improves performance. The memory controllerMemory controller
The memory controller is a digital circuit which manages the flow of data going to and from the main memory. It can be a separate chip or integrated into another chip, such as on the die of a microprocessor...
, which handles communication between the CPU and RAM, were moved onto the processor die
Die (integrated circuit)
A die in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated.Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon or other semiconductor through processes such as...
by AMD beginning with their AMD64 processors and by Intel with their Nehalem processors. One of the advantages of having the memory controller integrated on the CPU die is to reduce latency from the CPU-to-Memory so the CPU can control the memory directly.
Another example of this kind of change is Nvidia
NVIDIA
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...
's nForce3
NForce3
The nForce3 chipset was created by Nvidia as a Media and Communications Processor. Specifically, it was designed for use with the Athlon 64 processor.- Features of the nForce3 :...
chipset for AMD64 systems that is a single chip. It combines all of the features of a normal southbridge
Southbridge (computing)
The southbridge is one of the two chips in the core logic chipset on a personal computer motherboard, the other being the northbridge. The southbridge typically implements the slower capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. In Intel chipset...
with an AGP
Accelerated Graphics Port
The Accelerated Graphics Port is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics. Since 2004 AGP has been progressively phased out in favor of PCI Express...
port and connects directly to the CPU. On nForce4
NForce4
The nForce4 is a motherboard chipset released by Nvidia in October, 2004. The chipset supports AMD 64-bit processors and Intel Pentium 4 LGA 775 processors.-nForce4/nForce4-4x:...
boards they consider this to be an MCP (Media Communications Processor).
Intel's "Sandy Bridge" processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller and graphics processing unit (GPU). This was a further evolution of the Westmere architecture, which also featured a CPU and GPU in the same package.
AMD Fusion
AMD Fusion
AMD Fusion is the marketing name for a series of APUs by AMD. There are two flavors of Fusion currently available, one with its CPU logic based on the Bobcat core and the other its CPU logic based on the 10h core. In both cases the GPU logic is HD6xxx, which itself is based on the mobile variant of...
processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller and graphics processing unit (GPU). This was an evolution of the AMD64, since the memory controller was integrated on the CPU die in the AMD64.
Northbridge and overclocking
The northbridge plays an important part in how far a computer can be overclockedOverclocking
Overclocking is the process of operating a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to...
, as its frequency is commonly used as a baseline for the CPU to establish its own operating frequency. This chip typically gets hotter as processor speed becomes faster, requiring more cooling. There is a limit to CPU overclocking
Overclocking
Overclocking is the process of operating a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to...
, as digital circuit
Digital circuit
Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...
s are limited by physical factors such as propagation delay
Propagation delay
Propagation delay is a technical term that can have a different meaning depending on the context. It can relate to networking, electronics or physics...
which increases with (among other factors) operating temperature
Operating temperature
An operating temperature is the temperature at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the...
; consequently most overclocking applications have software-imposed limits on the multiplier
Frequency multiplier
In electronics, a frequency multiplier is an electronic circuit that generates an output signal whose output frequency is a harmonic of its input frequency. Frequency multipliers consist of a nonlinear circuit that distorts the input signal and consequently generates harmonics of the input signal...
and external clock setting. See Overclocking
Overclocking
Overclocking is the process of operating a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to...