Glossary - Computer Motherboards
Dimensions / Mounting Holes / Chipset / Processor slot/socket
/ AGP / PCI / ISA / RAM / Port / Serial / Parallel / PS/2 / USB / VGA / SCSI / Jumper / Connector header / Jumper header
/ BIOS / Driver / Cable set
/ Processor / System RAM / Chassis / Power Supply / Socket 7 / Socket 8 / Slot
1 / Slot 2 / Xeon / Cache
/ L1 Cache / L2 Cache / ACPI
/ SOHO / ECP / EPP / ECC / APM / DMI / SDRAM
/ EDO / DIMM / SIMM
Intel 810 / Intel 440BX / Intel 440GX / Intel 440LX / Intel 440ZX / ALi 1541 / SiS
530 / SiS 600 / VIA Apollo Pro
Baby AT (BAT) / ATX / MicroATX
Motherboard - the principle printed circuit board
assembly in a computer; includes core logic (chipset), interface sockets and/or slots, and
input/output (I/O) ports.
Printed circuit board (PCB) - a thin, laminated sheet composed of a series of epoxy
resin and copper layers and etched electronic circuits (signal, ground and power)
Chipset (or core logic) - two or more integrated circuits
which control the interfaces between the system processor, RAM, I/O devises, and adapter
Processor slot/socket - the slot or socket used
to mount the system processor on the motherboard
AGP - Accelerated Graphics Port - a high speed interface for
video cards; runs at 1X (66MHz), 2X (133MHz), or 4X (266MHz).
PCI - Peripheral Component Interconnect - a high speed interface
for video cards, sound cards, network interface cards, and modems; runs at 33MHz.
ISA - Industry Standard Architecture - a relatively low speed
interface primarily used for sound cards and modems; runs at approx. 8MHz.
RAM - Random Access Memory - see System RAM
Port (serial, parallel, PS/2, USB, sound, LAN, VGA, SCSI) -
interface connectors for the associated types of devices
Serial - a low speed interface typically used for mice and
Parallel - a low speed interface typically used for printers
PS/2 - a low speed interface used for mice and keyboards
USB - Universal Serial Bus - a medium speed interface typically
used for mice, keyboards, scanners, display panels (control features, not data), speakers
(control features, not sound), scanners, and some digital cameras.
VGA - Video Graphics Adapter - the interface from your video card
or integrated video connector and the system display monitor.
SCSI (interface) - Small Computer System Interface - the
interface between a SCSI controller and an external or internal SCSI device.
Jumper - a small block (approx .250" wide x .312"
long x .125" thick with two holes running lengthwise which are connected with a metal
structure), or the functionally equivalent electronic "interconnect"; used to
enable, disable, or select operating parameter on a motherboard or other PCB by
either electrically connecting two pins on the PCB (closed) or separating them (open -
only one pin is covered or the jumper is removed).
Connector header - a series of two or more metal
pins on the motherboard or other PCB; used to attach a cable to indicator lights,
switches, and/or other devices in the computer
Jumper header - two pins or a series of two-pin groups
where jumpers are used.
BIOS - Pronounced "bye-ose," an acronym for basic
input/output system. The BIOS is built-in software that determines what a computer can do
without accessing programs from a disk. On PCs, the BIOS contains all the code required to
control the keyboard, display screen, disk drives, serial communications, and a number of
The BIOS is typically placed in a ROM chip that comes with the computer (it is often
called a ROM BIOS). This ensures that the BIOS will always be available and will not be
damaged by disk failures. It also makes it possible for a computer to boot itself. Because
RAM is faster than ROM, though, many computer manufacturers design systems so that the
BIOS is copied from ROM to RAM each time the computer is booted. This is known as
Many modern PCs have a flash BIOS, which means that the BIOS has been recorded on a flash
memory chip, which can be updated if necessary.
The PC BIOS is fairly standardized, so all PCs are similar at this level (although there
are different BIOS versions). Additional DOS functions are usually added through software
modules. This means you can upgrade to a newer version of DOS without changing the BIOS.
PC BIOSes that can handle Plug-and-Play (PnP) devices are known as PnP BIOSes, or
PnP-aware BIOSes. These BIOSes are always implemented with flash memory rather than ROM.
Driver - software which defines the characteristics of a
device for use by another device or other software
Cable set - one or more interface cables (typically, in
relation to a motherboard, includes cables for a floppy drive, hard drive, and CD-ROM
drive; may include cables between an internal connector header and a bracket or other
opening at the front of rear of the system; may include cables for both IDE/ATAPI and SCSI
Processor - the "central processing unit" (CPU);
the principle integrated circuit used for doing the "computing" in
System RAM - the random access memory (RAM) used by the
CPU for computational purposes
Chassis - the structure used to house the various
"internal" components of the computer (i.e., the motherboard, adapter cards,
various storage devices, power supply, etc.) Normally called case.
Power Supply - the device used to convert, regulate, and
transmit external power for use by the components housed inside the computer chassis.
Socket 7 - The form factor for fifth-generation CPU chips
from Intel, Cyrix, and AMD. All Pentium chips, except Intel's Pentium Pro (Socket 8) and
Pentium II (Slot 1), conform to the Socket 7 specifications. Intel has decided to phase
out Socket 7 and replace it with Slot 1. But Intel's competitors, such as AMD and Cyrix,
are sticking with Socket 7, and are developing an enhanced version.
Socket 8 - The form factor for Intel's Pentium Pro
microprocessors. The Pentium Pro was the first microprocessor not to use the venerable
Socket 7 form factor. The Pentium II microprocessors use an even newer form factor called
Socket 8 is a 387-pin ZIF socket with connections for the CPU and one or two SRAM dies for
the Level 2 (L2) cache.
Slot 1 - The form factor for Intel's Pentium II processors.
The Slot 1 package replaces the Socket 7 and Socket 8 form factors used by previous
Pentium processors. Slot 1 is a 242-contact daughtercard slot that accepts a
microprocessor packaged as a Single Edge Contact (SEC) cartridge. A motherboard can have
one or two Slot 1s.
Slot 2 - A chip packaging design used in Intel's newer Pentium
II chipsets, starting with the Xeon CPU. While the Slot 1 interface features a 242-contact
connector, Slot 2 uses a somewhat wider 330-contact connector. The biggest difference
between Slot 1 and Slot 2, though, is that the Slot 2 design allows the CPU to communicate
with the L2 cache at the CPU's full clock speed. In contrast, Slot 1 only supports
communication between the L2 cache and CPU at half the CPU's clock speed.
Xeon - A line of Pentium II chipsets from Intel introduced in
1998. Unlike previous Pentium II chips, which used a Slot 1 form factor, Xeon chips use
Slot 2. This allows for faster data transfers between the CPU and L2 cache. Xeon chip
speeds start at 400 MHz.
Cache - Pronounced cash, a special high-speed storage
mechanism. It can be either a reserved section of main memory or an independent high-speed
storage device. Two types of caching are commonly used in personal computers: memory
caching and disk caching.
A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made
of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used
for main memory. Memory caching is effective because most programs access the same data or
instructions over and over. By keeping as much of this information as possible in SRAM,
the computer avoids accessing the slower DRAM.
Some memory caches are built into the architecture of microprocessors. The Intel 80486
microprocessor, for example, contains an 8K memory cache, and the Pentium has a 16K cache.
Such internal caches are often called Level 1 (L1) caches. Most modern PCs also come with
external cache memory, called Level 2 (L2) caches. These caches sit between the CPU and
the DRAM. Like L1 caches, L2 caches are composed of SRAM but they are much larger.
Disk caching works under the same principle as memory caching, but instead of using
high-speed SRAM, a disk cache uses conventional main memory. The most recently accessed
data from the disk (as well as adjacent sectors) is stored in a memory buffer. When a
program needs to access data from the disk, it first checks the disk cache to see if the
data is there. Disk caching can dramatically improve the performance of applications,
because accessing a byte of data in RAM can be thousands of times faster than accessing a
byte on a hard disk.
When data is found in the cache, it is called a cache hit, and the effectiveness of a
cache is judged by its hit rate. Many cache systems use a technique known as smart
caching, in which the system can recognize certain types of frequently used data. The
strategies for determining which information should be kept in the cache constitute some
of the more interesting problems in computer science.
L1 Cache - Short for Level 1 cache, a memory cache built
into the microprocessor. See under cache. The L1 cache is also called the primary cache.
L2 Cache - Short for Level 2 cache, cache memory that is
external to the microprocessor. In general, L2 cache memory, also called the secondary
cache, resides on a separate chip from the microprocessor chip. The Pentium Pro, however,
has an L2 cache on the same chip as the microprocessor.
ACPI - Short for Advanced Configuration and Power Interface, a
power management specification developed by Intel, Microsoft, and Toshiba. ACPI, which
will be part of the next version of Windows, enables the operating system to control the
amount of power given to each device attached to the computer. With ACPI, the operating
system can turn off peripheral devices, such as a CD-ROM players, when they're not in use.
As another example, ACPI will enable manufacturers to produce computers that automatically
power up as soon as you touch the keyboard.
APM - Short for Advanced Power Management, an API developed by
Intel and Microsoft that allows developers to include power management in BIOSes. APM
defines a layer between the hardware and the operating system that effectively shields the
programmer from hardware details.
APM is expected to be gradually replaced by ACPI.
SOHO - Acronym for Small Office/Home Office, the fastest growing
market for computer hardware and software. So-called SOHO products are specifically
designed to meet the needs of professionals who work at home or in small offices.
ECP - Short for Extended Capabilities Port, a parallel-port
standard for PCs that supports bi-directional communication between the PC and attached
devices (such as a printer). ECP is about 10 times faster than the older Centronics
Another modern parallel port for PCs that offers similar performance is the EPP (Enhanced
EPP - Short for Enhanced Parallel Port, a parallel port standard
for PCs that supports bi-directional communication between the PC and attached devices
(such as a printer). EPP is about 10 times faster than the older Centronics standard.
Another modern parallel port for PCs that offers similar performance is the ECP (Extended
ECC - Short for Error-Correcting Code memory, a type of memory
that includes special circuitry for testing the accuracy of data as it passes in and out
DMI - Short for Desktop Management Interface, an API to enable
software to collect information about a computer environment. For example, using DMI a
program can determine what software and expansion boards are installed on a computer.
DMI is designed to be platform -independent and operating system -independent so that
programs can make the same function calls to collect information no matter what system
they're running in. This system independence is implemented by collecting information from
MIF files, which are plain text files containing information about a software or hardware
DMI was designed by the Desktop Management Task Force (DMTF), a consortium of hardware
manufacturers led by Intel. Version 2.0 allows a central computer not only to gather
information about computers connected to a network, but also to configure them. PCs that
comply with DMI 2.0 are sometimes called managed PCs.
SDRAM - Short for Synchronous DRAM, a new type of DRAM that can
run at much higher clock speeds than conventional memory. SDRAM actually synchronizes
itself with the CPU's bus and is capable of running at 100 MHz, about three times faster
than conventional FPM RAM, and about twice as fast EDO DRAM and BEDO DRAM. SDRAM is
replacing EDO DRAM in many newer computers
Today's fastest Pentium systems use CPU buses running at 100 MHz, so SDRAM can keep up
with them, though barely. Future PCs, however, are expected to have CPU buses running at
200 MHz or faster. SDRAM is not expected to support these high speeds which is why new
memory technologies, such as RDRAM and SLDRAM, are being developed.
EDO - Short for Extended Data Output Dynamic Random Access
Memory, a type of DRAM that is faster than conventional DRAM. Unlike conventional DRAM
which can only access one block of data at a time, EDO RAM can start fetching the next
block of memory at the same time that it sends the previous block to the CPU.
DIMM - Short for dual in-line memory module, a small circuit
board that holds memory chips. A single in-line memory module (SIMM) has a 32-bit path to
the memory chips whereas a DIMM has 64-bit path. Because the Pentium processor requires a
64-bit path to memory, you need to install SIMMs two at a time. With DIMMs, you can
install memory one DIMM at a time.
SIMM - Acronym for single in-line memory module, a small circuit
board that can hold a group of memory chips. Typically, SIMMs hold up 8 (on Macintoshes)
or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking.
Unlike memory chips, SIMMs are measured in bytes rather than bits. SIMMs are easier to
install than individual memory chips.
The bus from a SIMM to the actual memory chips is 32 bits wide. A newer technology, called
dual in-line memory module (DIMM), provides a 64-bit bus. For modern Pentium
microprocessors that have a 64-bit bus, you must use either DIMMs or pairs of SIMMs.
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Chipset Models - Today there are many chipset
models in the marketplace. The most popular for mainstream desktop computers are Intel's
810, BX, LX, and ZX. There are also "third party" chipsets available from Acer
Labs (ALi), Silicon Integrated Systems (SiS), and VIA Technologies (VIA). The latter are
quite similar to their Intel counterparts but may add features not available in the Intel
chipsets. The third party chipsets may also support non-Intel processors (like those from
AMD and others that have a 100MHz data bus and use the "Socket 7"
processor-to-motherboard socket). Intel also produces chipsets that support dual
processors. [At the time this FAQ was prepared, only Intel was producing chipsets which
support multiple processors.] The following are brief descriptions of the key features of
the most popular primary Intel and third party chipsets as of the date this FAQ was
prepared (mid-June '99).
Intel 810 - "Basic PC and Mainstream segments",
supports 2 DIMM (max. 512MB), SDRAM only, ECC/parity not supported, integrated
"direct" AGP, integrated graphics controller (enhanced i740), 66/100MHz data
bus, Ultra ATA/66 device support.
Intel 440BX - "Performance segment", supports 4
DIMM (max 1GB), SDRAM only, ECC/parity supported, AGP 2X, 66/100MHz data bus, Ultra
ATA/33 device support; dual processor support.
Intel 440GX - "Workstation segment", supports 4
DIMM (max 2GB), SDRAM only, ECC/parity supported, AGP 2X, 100MHz data bus, Ultra ATA/33
device support; dual processor support; supports Pentium II/III and Pentium Xeon II/III
Intel 440LX - "Basic PC segment", supports 4
DIMM (max 512MB SDRAM, 1GB EDO), ECC/parity supported, AGP 2X, 66MHz data bus, Ultra
ATA/33 device support; dual processor support
Intel 440ZX - "Mainstream segment", supports 2
DIMM (max 256MB), SDRAM only, ECC/parity not supported, AGP 2X, 66/100MHz data bus, Ultra
ATA/33 device support.
ALi 1541 - mainstream (Socket 7), supports 3 DIMM, 100MHz
data bus, AGP 2X
SiS 530 - mainstream (Socket 7), supports 3 DIMM, 100MHz data
bus, AGP 2X, integrated graphics controller
SiS 600 - mainstream (Pentium II/III), supports 3 DIMM, 100MHz
data bus, AGP 2X
VIA Apollo Pro - mainstream (Pentium II/III), supports 4
DIMM, 100MHz data bus, AGP 2X
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Form Factor - the physical layout of a motherboard in
regards the relative position of the adapter card expansion slots, the number of those
slots, the relative size of the motherboard, and the orientation of the board in the
chassis . For the purpose of this FAQ, only the Baby AT (BAT), ATX, and MicroATX form
factors will be considered.
Baby AT (BAT) - this is the oldest of the currently available,
mainstream motherboard form factors. Its distinguishing features are its orientation in
the chassis (the long axis goes from the back to the front of the chassis), the type of
keyboard connector (typically referred to as a "large DIN" connector), the
presence of AT or PS/2 power supply connectors (a series of 12 "blades" in one
or two adjacent male connectors), and the implementation of the various I/O connectors
(serial and parallel ports) via a bracket which goes into one of the adapter card slots at
the rear of the chassis. Please note that in some motherboards there may also be an ATX
power supply connector (a rectangular grouping of 20 small sockets in two adjacent rows of
ATX - this is the most common of today's mainstream motherboard
form factors. Its distinguishing features are its orientation in the chassis (the long
axis goes from side-to-side at the rear of the chassis), the use of "integrated I/O
connectors" (all the connectors are built into the motherboard and exit to the rear
of the chassis through an "I/O shield" where they are grouped together), and
only an ATX power supply connector is provided.
MicroATX - this is a variation of the ATX form factor. It is
much shorter in its long axis than the ATX and has fewer adapter card slots (3 compared to
the ATX with typically 7). Otherwise the features are the same as the ATX.
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- BTX 12.8" × 10.5" (325 mm × 267 mm max)
A standard proposed by Intel as a successor to ATX in the early 2000s, according to Intel the layout has better cooling. BTX Boards are flipped in comparison to ATX Boards, so a BTX or MicroBTX Board needs a BTX case, while an ATX style board fits in an ATX case.
The BTX form factor motherboards are incompatible with most of the ATX form factor cases and vice-versa. Moreover, cases such as the Cooler Master Series (Stackers) support a varying range of motherboard types such as ATX, BTX, Mini-ATX and so forth. However, all connectors are compatible, including power supplies, PCI cards, processors, RAM, hard drives, etc.
- MicroBTX 10.4x10.5" (264x267mm)
- EATX(Extended ATX ) 12" × 13"(305mm × 330 mm)
Used in rackmount server systems. Typically used for server-class type motherboards with dual processors and too much circuitry for a standard ATX motherboard. The mounting hole pattern for the upper portion of the board matches ATX.
- ATX 12" × 9.6" (305 mm × 244 mm)
Created by Intel in 1995. As of 2007, it is the most popular form factor for commodity motherboards. Typical size is 9.6x12" although some companies extend that to 10x12".
- microATX 9.6" × 9.6" (244 mm × 244 mm)
A smaller variant of the ATX form factor (about 25% shorter). Compatible with most ATX cases, but has fewer slots than ATX, for a smaller power supply unit. Very popular for desktop and small form factor computers as of 2007.
- FlexATX 9.0" x 7.5" (228.6 × 190.5 mm max)
It is a motherboard form factor derived from ATX. The specification was released in 1999 by Intel as an addendum to the microATX specification. It uses a subset of the motherboard mounting holes required for microATX and the same I/O plate system as ATX and microATX.
FlexATX specifies that a motherboard be no larger than 9.0 x 7.5" (229 x 191 mm), and can have no more than 2 expansion slots.
- Mini-ATX 5.9" × 5.9" (150 mm × 150 mm)
Mini-ATX is slightly smaller than Mini-ITX. Mini-ATX motherboards were design with MoDT (Mobile on Desktop Technology) which adapt mobile CPU for lower power requirement and less heat generation, which makes them ideal for home theater PC (HTPC) and car PC for consumer and application PC for industrial.
- SSI CEB 12" × 10.5" (305 mm × 267 mm)
Created by the Server System Infrastructure (SSI) forum. Derived from the EEB and ATX specifications. This means that SSI CEB motherboards have the same mounting holes and the same IO connector area as ATX motherboards.
- Mini-ITX 6.7" × 6.7" (170 mm × 170 mm max)
A small, highly-integrated form factor, designed for small devices such as thin clients and set-top boxes.
- Nano-ITX 4.7" × 4.7" (120 mm × 120 mm)
Targeted at smart digital entertainment devices such as PVRs, set-top boxes, media centers and Car PCs, and thin devices.
Reference: WikipediA Computer form factor
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FlexATX, microATX and ATX Mounting Holes:
||Mounting Hole locations
||B, C, F, H, J, S
||B, C, F, H, J, L, M, R, S
||Holes R and S were added for microATX form factor.
Hole B was defined in Full AT format
||A C F G H J K L M
||Hole F must be implemented in all ATX2.03-compliant chassis assemblies. The hole was optional in the ATX 1.1 specificatio.
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