North Bridge

Northbridge (computing) The northbridge, also known as a memory controller hub (MCH) or an integrated memory controller (IMC) in Intel systems (AMD, VIA, SiS and others usually use 'northbridge'), is one of the two chips in the core logic chipset on a PC motherboard, the other being the southbridge. Separating the chipset into the northbridge and southbridge is common, although there are rare instances where these two chips have been combined onto one die when design compleOverview The northbridge typically handles communications among the CPU, RAM, AGP or PCI Express, and the southbridge.[1][2] 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 signalling, a 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. [edit] 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. Intel i815EP northbridge [edit] Importance The northbridge on a particular system's motherboard is the most prominent factor in dictating the number, speed, and type of CPU(s) and the amount, speed, and type of RAM that can be used. Other factors such as voltage regulation and available number of connectors also play a role. Virtually all consumer-level chipsets support only one processor series, with the maximum amount of RAM varying by processor type and motherboard design. Pentium-era machines often had a limitation of 128 MB, while most Pentium 4 machines have a limit of 4 GB. Since the Pentium Pro, the Intel architecture can accommodate physical addresses larger than 32 bits, typically 36 bits, which gives up to 64 GB of addressing (see PAE), though motherboards that can support that much RAM are rare because of other factors (operating system limitations and expense of RAM). A northbridge typically will only work with one or two different southbridges. In this respect, it affects some of the other features that a given system can have by limiting which technologies are available on its southbridge partner.

The northbridge hosts its own memory lookup table (I/O memory management unit), a mapping of the addresses and layout in main memory. The northbridge handles data transactions for the front side bus (FSB), the memory bus and the AGP port. The northbridge will have a different model number, even though they are often paired with the same southbridge to come under the collective name of the chipset. The Intel Hub Architecture(IHA) has replaced the northbridge/southbridge chipset. The IHA chipset also has two parts: the Graphics and AGP Memory Controller Hub (GMCH) and the I/O Controller Hub (ICH). The IHA architecture is used in Intel's 800 series chipsets, which is the first x86 chipset architecture to move away from the northbridge/southbridge design. [edit] Recent developments The memory controller, which handles communication between the CPU and RAM, has been moved onto the processor die in AMD64 processors. Intel has integrated the memory controller onto the processor die with their Nehalem microarchitecture-based processors. 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). [edit] Northbridge and overclocking The northbridge plays an important part in how far a computer can be overclocked, as its frequency is used as a baseline for the CPU to establish its own operating frequency. In today's machines, this chip is becoming increasingly hotter as computers become faster and thus also requires an increased level of cooling. xity and fabrication processes permit it.

Southbridge (computing) A typical north/southbridge layout The Southbridge, also known as an I/O Controller Hub (ICH) or a Platform Controller Hub (PCH) in Intel systems (AMD, VIA, SiS and others usually use 'southbridge'), is a chip that implements the "slower" capabilities of the motherboard in a northbridge/southbridge chipset computer architecture. The southbridge can usually be distinguished from the northbridge by not being directly connected to the CPU. Rather, the northbridge ties the southbridge to the CPU.

Overview Because the southbridge is further removed from the CPU, it is given responsibility for the slower devices on a typical microcomputer. A particular southbridge will usually work with several different northbridges, but these two chips must be designed to work together; there is no industry-wide standard for interoperability between different core logic chipset designs. Traditionally this interface between northbridge and southbridge was simply the PCI bus, but since this created a performance bottleneck, most current chipsets use a different (often proprietary) interface with higher performance. [edit] Etymology The name is derived from drawing the architecture in the fashion of a map and was first described as such with the introduction of the PCI Local Bus Architecture into the PC platform in 1991. The authors of the PCI spec at Intel

viewed the PCI local bus as being at the very center of the PC platform architecture (i.e., at the Equator). The so called Northbridge extends to the north of PCI in support of CPU, Memory/Cache and other performance critical capabilities. Likewise the Southbridge extends to the south of the PCI bus backbone and bridged to less performance critical I/O capabilities such as the disk interface, audio, etc. The PCI unit would be at the top of the map at due north. 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. Note that current day PC platform architecture has replaced PCI with a faster I/O backbone however the bridge naming convention remains. [edit] Functionality The functionality found on a contemporary southbridge includes:

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PCI bus. The PCI bus support includes the traditional PCI specification, but may also include support for PCI-X and PCI Express.

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ISA bus or LPC Bridge. Though the ISA support is rarely utilized, it has interestingly managed to remain an integrated part of the modern southbridge. The LPC Bridge provides a data and control path to the Super I/O (the normal attachment for the keyboard, mouse, parallel port, serial port, IR port, and floppy controller) and FWH (firmware hub which provides access to BIOS flash storage).

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SPI bus. The SPI bus is a simple serial bus mostly used for firmware (e.g., BIOS) flash storage access.

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SMBus. The SMBus is used to communicate with other devices on the motherboard (e.g. system temperature sensors, fan controllers).

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DMA controller. The DMA controller allows ISA or LPC devices direct access to main memory without needing help from the CPU.

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Interrupt controller. The interrupt controller provides a mechanism for attached devices to get attention from the CPU.

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IDE (SATA or PATA) controller. The IDE interface allows direct attachment of system hard drives.

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Real-time clock. The real time clock provides a persistent time account.

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Power management (APM and ACPI). The APM or ACPI functions provide methods and signaling to allow the computer to sleep or shut down to save power.

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Nonvolatile BIOS memory. The system CMOS, assisted by battery supplemental power, creates a limited non-volatile storage area for system configuration data.

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AC97 or Intel High Definition Audio sound interface

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Baseboard Management Controller

Optionally, the southbridge will also include support for Ethernet, RAID, USB, audio codec, and FireWire. Rarely, the southbridge may also include support for the keyboard, mouse, and serial ports, but normally these devices are attached through another device referred to as the Super I/O.

what does your Motherboard Chipset actually do? We have all heard about the latest chipsets from Intel, VIA, Nvidia and more and how much better they are. But what does the chipset actually do on the motherboard. We know what the CPU does, we know what the graphics card is for and why we have a hard disk drive but not many people know too much about the chipset. Hopefully we can shed a little light on the working of the chipset and why they differ from one chipset to the next.

North and South bridge? The chipset consists of two major microchips. These are known as the North bridge and the South Bridge. The North Bridge Handles data for the AGP Port and the main memory which includes the FSB (Front side bus). Although both chips are required for the PC to work the North Bridge handles most of the very important tasks such as the connection between the CPU and main memory. The South Bridge handles data from the PCI and ISA slots and can also have integrated components such as Audio codec's etc. The North and South bridges will have different chip names even though they are very often paired with the same opposite bridge to come under the collective name of the chipset. Below is a diagram of the KT600 chipset from VIA technologies. This diagram shows how the components of your PC are connected to the chipset. Catch the Bus The function of a chipset is to manage data throughput. All data that your components require or acquire need to be transported. They are transported by what's known as a bus. The bus carry's the data to where it needs to go via the chipset. The exception to rule here is the BSB (Back side bus) the BSB is the bus between the CPU and the cache memory. Today's CPU's have the cache memory "on-chip" and so there is no need to go through the chipset. The BSB is not to get confused with the main memory bus. The BSB only dictates the speed between the CPU and the cache memory. The memory bus speed is on a different bus and this speed can be changed independently. Excluding the BSB all other buses go through the chipset in order to get direction for where it needs to take the data. Because of the amount of data that goes through the chipset it is important that the chipset is up to speed. What Chipset? Since we now know that the chipset handles an incredible amount of data, its important to see which chipsets are performing the best. Firstly to choose a chipset that supports your CPU. You obviously cant have a chipset designed for an Intel CPU if your using an Athlon XP. Then the best way to see which chipsets are performing the best is to look at benchmarks on various sites. A slow chipset can be as damaging to your systems overall speed as a slow CPU or slow memory. The slowest component always dictates the overall speed at any given time. If you have a poor performing chipset, then any time that your computer is sending and receiving data from the graphics card or main memory, then the system is struggling