In computing, a northbridge (also host bridge, or memory controller hub) is one of two chips comprising the core logic
chipset architecture on a
PC motherboard
A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...
. A northbridge is connected directly to a
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
via the
front-side bus (FSB) to handle high-performance tasks, and is usually used in conjunction with a slower
southbridge to manage communication between the
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
and other parts of the motherboard. Since the 2010s,
die shrink
The term die shrink (sometimes optical shrink or process shrink) refers to the scaling of metal-oxide-semiconductor (MOS) devices. The act of shrinking a die is to create a somewhat identical circuit using a more advanced fabrication process, u ...
and improved
transistor density
The transistor count is the number of transistors in an electronic device (typically on a single substrate or "chip"). It is the most common measure of integrated circuit complexity (although the majority of transistors in modern microprocesso ...
have allowed for increasing chipset integration, and the functions performed by northbridges are now often incorporated into other components (like southbridges or CPUs themselves).
As of 2019,
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...
and
AMD had both released chipsets in which all northbridge functions had been integrated into the CPU.
Modern Intel Core processors have the northbridge integrated on the CPU die, where it is known as the
uncore or system agent.
On older Intel based PCs, the northbridge was also named external memory controller hub (''MCH'') or graphics and memory controller hub (''GMCH'') if equipped with integrated graphics. Increasingly these functions became integrated into the CPU chip itself,
beginning with memory and graphics controllers. For
Intel Sandy Bridge and
AMD Accelerated Processing Unit processors introduced in 2011, all of the functions of the northbridge reside on the CPU. The corresponding southbridge was renamed by Intel as the
Platform Controller Hub and by AMD as the
Fusion controller hub
This is an overview of chipsets sold under the AMD brand, manufactured before May 2004 by the company itself, before the adoption of open platform approach as well as chipsets manufactured by ATI Technologies after October 2006 as the completion ...
. AMD FX CPUs continued to require external northbridge and southbridge chips.
Historically, separation of functions between CPU, northbridge, and southbridge chips was necessary due to the difficulty of integrating all components onto a single
chip die. However, as CPU speeds increased over time, a
bottleneck
Bottleneck literally refers to the narrowed portion (neck) of a bottle near its opening, which limit the rate of outflow, and may describe any object of a similar shape. The literal neck of a bottle was originally used to play what is now known as ...
emerged due to limitations caused by data transmission between the CPU and its support chipset. The trend for integrated northbridges began near the end of the
2000s — for example, the
Nvidia GeForce 320M GPU in the 2010 MacBook Air was a northbridge/southbridge/GPU combo chip.
Overview
The northbridge typically handles communications among the
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
, in some cases
RAM, and
PCI Express
PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common ...
(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 made available when there is a shift to a new standard. For example, the northbridge from the 2002
Nvidia
Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...
nForce2 chipset only worked with
Socket A processors combined with
DDR SDRAM.
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
chipset 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.
Overclocking
The northbridge plays an important part in how far a computer can be
overclocked, 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 In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathemati ...
s are limited by physical factors such as rise, fall, delay and storage times of the
transistors
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
, current gain bandwidth product,
parasitic capacitance
Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other. When two electrical conductors at different voltages ...
, and
propagation delay, which increases with (among other factors)
operating temperature
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...
; consequently most overclocking applications have software-imposed limits on the
multiplier and external clock setting. Additionally, heat is a major limiting factor, as higher voltages are needed to properly activate
field effect transistors inside CPUs and this higher voltage produces larger amounts of heat, requiring greater thermal solutions on the die.
Evolution
The overall trend in processor design has been to integrate more functions onto fewer components, which decreases overall motherboard cost and improves performance. The
memory controller, which handles communication between the CPU and RAM, was moved onto the processor
die
Die, as a verb, refers to death, the cessation of life.
Die may also refer to:
Games
* Die, singular of dice, small throwable objects used for producing random numbers
Manufacturing
* Die (integrated circuit), a rectangular piece of a semicondu ...
by AMD beginning with their
AMD K8
The AMD K8 Hammer, also code-named SledgeHammer, is a computer processor microarchitecture designed by AMD as the successor to the AMD K7 Athlon microarchitecture. The K8 was the first implementation of the AMD64 64-bit extension to the x86 inst ...
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.
Another example of this kind of change is
Nvidia
Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...
's
nForce3 for
AMD K8
The AMD K8 Hammer, also code-named SledgeHammer, is a computer processor microarchitecture designed by AMD as the successor to the AMD K7 Athlon microarchitecture. The K8 was the first implementation of the AMD64 64-bit extension to the x86 inst ...
systems. It combines all of the features of a normal
southbridge with an
Accelerated Graphics Port (AGP) port and connects directly to the CPU. On
nForce4
The nForce4 is a motherboard chipset released by Nvidia in October 2004. The chipset supports AMD 64-bit processors (Socket 939, Socket AM2 and Socket 754) and Intel Pentium 4 LGA 775 processors.
Models nForce4/nForce4-4x
nForce4 is the second ...
boards it was marketed as a media communications processor (MCP).
AMD Accelerated Processing Unit processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller, high speed
PCI Express
PCI Express (Peripheral Component Interconnect Express), officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common ...
interface (usually for graphics card), and integrated graphics processing unit (iGPU). This was an evolution of the
AMD K8
The AMD K8 Hammer, also code-named SledgeHammer, is a computer processor microarchitecture designed by AMD as the successor to the AMD K7 Athlon microarchitecture. The K8 was the first implementation of the AMD64 64-bit extension to the x86 inst ...
, since the memory controller was integrated on the CPU die in the AMD64.
The northbridge was replaced by the system agent introduced by the Intel
Sandy Bridge microarchitecture
In computer engineering, microarchitecture, also called computer organization and sometimes abbreviated as µarch or uarch, is the way a given instruction set architecture (ISA) is implemented in a particular processor. A given ISA may be imp ...
in 2011, which essentially handles all previous Northbridge functions. Intel's Sandy Bridge processors feature full integration of northbridge functions onto the CPU chip, along with processor cores, memory controller, high speed PCI Express interface and integrated
graphics processing unit
A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, m ...
(GPU). This was a further evolution of the Westmere architecture, which also featured a CPU and GPU
in the same package.
Recent AMD processors starting with the
Zen 2
Zen 2 is a computer processor microarchitecture by AMD. It is the successor of AMD's Zen and Zen+ microarchitectures, and is fabricated on the 7 nanometer MOSFET node from TSMC. The microarchitecture powers the third generation of Ryzen proces ...
have moved some I/O functions out of the CPU die onto an I/O die on the same
MCM package as the CPU. This die is not normally considered to be part of the Northbridge, since it's in the same package as the CPU, but it serves some of the same functions.
See also
*
Southbridge
*
Chipset
*
Intel Management Engine (ME)
References
{{Reflist
IBM PC compatibles
Chipsets