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Motherboard Glossary

Motherboard Glossary

Table of contents


AC '97

AC '97 (Audio Codec '97) is the audio standard/architecture developed by Intel in 1997. It delivers multichannel 16-bit, 48 KHz recording and playback, with optional support of 18-bit and 20-bit resolution and up to 96 KHz sampling frequency (stereo). AC '97 is widely used in on-board audio, modems and sound cards.


The AGP (Accelerated Graphics Port) slot on the computer motherboard is designed specifically for AGP graphics cards. AGP 8X can provide 16 times the bandwidth of the common 32-bit PCI slot. AGP is currently being phased out in favor of PCI Express on PC systems.


AGP Pro is an extension to the AGP interface specification; it is designed to meet the increasing power requirement of workstation level graphics cards by delivering additional electrical power. AGP Pro graphics cards and slots are often longer than their standard AGP counterparts.

Developed by Intel in 1995, ATX (Advanced Technology Extended) was designed to replace the AT/Baby AT form factor. An ATX motherboard is essentially a Baby AT motherboard rotated 90 degrees within the case with a new mounting configuration for the power supply so that the IDE connectors are closer to the drive bays and the CPU is closer to the power supply and cooling fan. There are many variants of the ATX form factor for smaller boards (such as microATX and Flex ATX), usually providing the basic rear layout but reducing the board size and the number of expansion slots.


The BIOS (Basic Input/Output System) refers to the program/software code residing in a ROM chip. It provides the basic instructions for booting up your computer and controlling computer hardware so other software programs such as the operating systems can be loaded and executed.


As the next-generation successor to the ATX form factor, the BTX (Balanced Technology Extended) form factor specifies a new layout for heat-generating components on the motherboard, to allow in-line airflow for system cooling, reducing the number of fans needed, offering thermal headroom for future high power components, and enabling a broader range of standards-based system designs. There are smaller-sized BTX form factors as well, such as microBTX and picoBTX.


The bus often refers to a data pathway (sometimes called the power pathway) which transfers data (or power) between computer components inside a computer system or between different computers. For example, there is a front side bus to connect the CPU to the chipset, and there is the PCI bus to connect the chipset to PCI devices.

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Chipset, covers Northbridge, Southbridge, (G)MCH, ICH

The term "chipset" (sometimes called core logic) often refers to the two main chips on the motherboard: the Northbridge and the Southbridge. The Northbridge and Southbridge are sometimes combined. This is called single-chip design. The Northbridge (MCH or Memory Controller Hub in Intel applications) often refers to the chip that handles communications between the CPU, and the AGP or PCI Express bus and the Southbridge. The Northbridge often includes the memory controller if the memory controller is not integrated into the CPU, and certain Northbridge chips feature integrated graphics units (Intel calls these Northbridge chips the GMCH or Graphics & Memory Controller Hub).

The Southbridge (Intel calls it the ICH or Input/Output Controller Hub) provides connections to I/O devices, such as the PCI bus, USB, PATA, SATA and PCI Express devices. Other Southbridge functions include interrupt controller, real time clock, power management (ACPI and APM), SMBus and so on. Southbridge chips are usually connected to Northbridge chips.


In motherboards the CMOS (Complementary Metal-Oxide Semiconductors) refers to the chips that contains the basic start-up information for the BIOS (aka BIOS settings).


In motherboards, the "codec" (Compressor-Decompressor or Coder-Decoder) or "audio codec" refers to the combined audio AD/DA (analog to digital/digital to analog) converter, which is a required hardware for most onboard audio solutions.

CPU Socket, Socket A/478/754/939/940, LGA775

The CPU socket or slot is the interface of both the processor and the motherboard. The processor's socket type must match the motherboard's CPU socket to be installed properly. For example, an LGA775 processor must be installed on an LGA775 motherboard.

Below are the major socket types for contemporary AMD motherboards:

Socket 754  Socket 939

Socket 754 processors include Sempron and some older model Athlon 64 processors, while Socket 939 is utilized by some AMD K8 desktop processors such as Athlon 64, Athlon 64 FX, and Athlon 64 X2.

Socket AM2

The latest Socket AM2 has been adopted by all AMD desktop processor families including Sempron, Athlon 64, Athlon 64 FX and Athlon 64 X2.

And here are the major socket types for contemporary Intel motherboards:

Socket 478  LGA775/Socket T

With the exception of certain Pentium 4 & Celeron D models still utilizing the Socket 478, most Intel processor products like the Celeron D, Pentium 4, Pentium D, and Pentium Extreme Edition are currently on the LGA775 socket.


DDR (Double Data Rate) SDRAM sends and receives data twice as often as common SDRAM. This is achieved by transferring data on both the rising edge and the falling edge of a clock cycle.


Second generation DDR memory provides greater bandwidth and other new features such as On-Chip Termination (OCT). 4 bits of data are moved from the memory array to the I/O buffers (per data line) each core cycle. This can be described as 4-bit prefetch, as opposed to the single-bit fetch in SDRAM and 2-bit prefetch with DDR SDRAM.


The most common type of memory module is the DIMM (Dual In-Line Memory Module), which is capable of transferring 64 bits of data per cycle.


The memory cells of DRAM (Dynamic Random Access Memory) memory modules require constant refreshing because they utilize both transistors and capacitors. Capacitors lose the values they store as time elapses without refreshing.


In the memory system, this describes a motherboard/memory controller with two 64-bit wide channels. When memory is used in dual channel mode, the bandwidth doubles - for instance, dual channel DDR400 provides 6400MB/s (or 6.4GB/s) bandwidth as opposed to 3200MB/s for single channel DDR400.


DVI (Digital Video Interface) is a display/monitor interface standard. There are three types DVI: DVI-I (digital and analog), DVI-D (digital only) and DVI-A (analog only). Many current display devices use DVI to receive video signals, such as LCD monitors and projectors. For compatibility with these display devices, most video cards today equip the DVI port as a standard output port.

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ECC (Error Checking and Correction) can be accomplished through a variety of methods. The most popular method utilized by memory modules is single bit error correction, which is capable of detecting and correcting single-bit errors. It will also detect two-bit and some multiple bit errors, but is unable to correct them.

Form factor

In computing, form factor is an industry term for the size, shape and format of computer motherboards, power supplies, cases, add-in cards and so on. The ATX and BTX form factors are the most prevalent form factors today.

HD Audio

Developed and released by Intel in 2004, the HD Audio (High Definition Audio) specification replaced the AC '97 specification. HD Audio based hardware can deliver up to eight sound channels at 192 kHz/32-bit quality, which is far better than AC '97. In addition, HD Audio prevents the occasional glitches or pops sometimes present in other audio solutions by using dedicated system bandwidth for critical audio functions.

IEEE 1394

Also known by the trademarked names of FireWire and i.LINK, IEEE 1394 is a standard for high-speed transfer of digital information. It is one of the most popular standards for connecting computers and other digital devices to various components and peripherals, such as external hard disk drives, scanners and digital video camcorders.


I/O (Input / Output) often refers to the connection or interface between your computer system and other internal or peripheral hardware devices.


ISA (Industry Standard Architecture) is a standard system bus which was introduced as an 8-bit bus with the original IBM PC in 1981. This was later expanded to 16-bit with the IBM PC/AT in 1984. ISA slots have been phased out.


A LAN (Local-Area Network) is a computer network that connects PCs, workstations or other LANs and networks to enable data and device access and sharing. It is used to cover a small local area such as a home, office or small group of buildings. Current LANs are most likely to be Ethernet (wired) or Wi-Fi (wireless) based.

Parallel Port or LPT

Originally called LPT, the Parallel Port is an interface in a computer system where data is transferred in parallel. It has been replaced by the USB port, and is considered to be a legacy port.


ATA is the acronym for Advanced Technology Attachment, and it has become an industry standard hard drive interface for 15 years. ATA uses a 16-bit parallel connection to make the link between storage devices and motherboards, and is also called PATA (Parallel ATA) to distinguish it from the newer SATA standard. In additional, ATA is also known as IDE or EIDE (Enhanced Integrated Drive Electronics). Currently the two most popular standards for ATA hard drives are the ATA-6 (which is also known as Ultra ATA 100 or Ultra DMA 100) and ATA 133. The maximum bandwidth for the former is 100MB/s, and 133 MB/s for the latter.


The PCI (Peripheral Component Interconnect) bus is a computer bus type used to connect computer peripherals. Most PCI buses in a PC system work at 33MHz with a 32bit bit-width. This allows it to deliver a bandwidth of 133MB/s.

The PCI slot (not to be mistaken with the PCI bus) has fallen out of favor in the graphics domain and has been replaced by the AGP and PCI Express connectors.

PCI Express

PCI Express is the latest computer bus following PCI and AGP. PCI Express can come in several physical configurations to offer a variety of maximum bandwidths. For example, the fastest PCI Express x16 configuration is used mainly for graphics card application and provides up to 8GB/s (bi-directional) bandwidth, or 4 times the bandwidth of AGP 8X. At the other end of the spectrum, PCI Express x1 is typically used for other types of peripherals and offers up to 500MB/s (bi-directional) bandwidth.


PCI-X was introduced to address the need for increased bandwidth of PCI devices. PCI-X specification enables higher operating frequency (66MHz,133MHz, 266MHz and even 533MHz) with up to 64-bit bit-width of the bus, so it is capable of delivering more than 1066MB/s of bandwidth. Furthermore, PCI-X protocol enhancements enabled devices to operate at much higher efficiency, providing more useable bandwidth at any given clock frequency.

PS/2 Ports

The Personal System/2 or PS/2 was the designation for IBM's second generation of personal computers. The PS/2 keyboard and mouse ports were introduced with it. PS/2 ports connect the keyboard and mouse to a computer and are usually color-coded on today's systems - purple for keyboards and green for mice. Most desktop motherboards still provide PS/2 ports, but an increasing number of keyboards and mice are using USB ports.

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RAID (Redundant Array of Independent/Inexpensive Disks) is a method of using multiple hard drives together for data storage. A RAID system with multiple hard drives appears as a single drive to the operating system. Depending on the RAID level, the benefits provided by RAID is one or more of the following: better throughput, fault-tolerance or capacity (or something else) when compared to single hard drive.

1. RAID level 0 (or RAID 0) is known as striping, where data is striped across multiple hard drives. RAID 0 provides the most advanced throughput and capacity, but offers no fault-tolerance.

2. RAID level 1 (RAID 1) is known as mirroring, which stores the exact same data within at least two hard drives, this method shows excellent fault-tolerance and reliability, but delivers less capacity efficiency.

3. RAID level 0+1 and RAID 1+0 are both striping and mirroring, providing good fault-tolerance and throughput all at the same time.

There are other RAID levels available too, such as RAID level 5 and RAID level 6.

Registered/Unbuffered Memory

Almost all system memory in today's PCs is unbuffered memory. With increasing system memory, the stability and performance deterioration of memory is inevitable since the memory controller has to address each memory chip on all modules directly. To solve this problem, higher density systems use registered memory instead which contains registers as buffer to temporarily hold data for one clock cycle before it is transferred. This increases the reliability of high-speed data access to high density memory. Registered memory modules are typically used only in servers and other mission-critical systems where it is extremely important that the data is properly handled.


SATA (Serial ATA) is an interface standard for connecting hard drives to computer systems, and is based on serial signaling technology. The advantages over PATA include longer, thinner cables for more efficient airflow within a computer chassis, fewer pin conductors for reduced electromagnetic interference, and lower signal voltage to minimize noise margin. The bandwidth of SATA is also far improved over today's PATA - the SATA 1.0 can reach a maximum of 1.5Gb/s (150MB/s), while the latest SATA 2.5 standard can support up to 3Gb/s (300MB/s). As a result of so many advantages, the SATA interface is gradually replacing PATA as the mainstream hard drive interface in the personal storage market.


SCSI (Small Computer System Interface) is a standard interface for transferring data between devices and computers. Thanks to its outstanding ability to compartmentalize diverse operation, SCSI is very suitable for multitasking operating environments. Also, SCSI enhances critical performance in situations where more than one device is connected. Before serial signaling technology was applied into the SCSI field, all SCSI interface standards used parallel technology to transfer data.


SDRAM (Synchronous Dynamic Random Access Memory) has a synchronous interface. It waits for a clock pulse before transferring data and is therefore synchronous with the computer system bus and processor. This greatly improves performance over asynchronous DRAM.

Serial Port, COM

Unlike parallel port, serial port (aka COM) is an interface on a computer system which transfers information one bit at a time. Most serial ports of personal computer uses RS-232 standard, and RS-232 is still commonly used in industry devices. Serial port has also been replaced by USB ports (and PS/2 ports).


S/PDIF (Sony/Philips Digital Interface) is a digital audio interface widely used in consumer electronics and sound cards. There are several different types of cables and connectors for S/PDIF:

1. Coaxial or RCA jack, digital audio information is transferred in the form of an electronic signal.

2. Optical or "TOSLINK", all information is transferred in optical signal form.


The USB (Universal Serial Bus) port is a popular I/O interface used for connecting computers and peripherals or other devices. It is capable of supporting up to 127 daisy-chained peripheral devices simultaneously. The latest USB 2.0 specification can deliver 480Mbps data transfer bandwidth.

VGA, D-Sub

This 15-pin VGA (Video Graphics Array) output port (aka D-sub) finds widespread usage and is used to connect a computer to CRT monitors and LCD monitors that support analog input. Digital signals must go through RAMDAC conversion before being sent through the D-Sub port as it is capable of only analog input.

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