Computer Form Factor

Overview of form factorsATX in the early 2000s, according to Intel the
A PC motherboard is the main circuit board withinlayout has better cooling. BTX Boards are flipped
a typical desktop computer, laptop or server. Itsin comparison to ATX Boards, so a BTX or
main functions are as follows:to serve as a centralMicroBTX Board needs a BTX case, while an ATX
backbone to which all other modular parts such asstyle board fits in an ATX case.
CPU, RAM, and hard drives can be attached asMicroBTX (or uBTX)
required to create a modern computer;to acceptIntel 2004
(on many motherboards) different components (in10.4  10.5 in
particular CPU and expansion cards) for the264  267 mm max.
purposes of customization;to distribute power toPicoBTX
PC components;to electronically co-ordinate andIntel 2004
interface the operation of the components.8.0  10.5 in
As new generations of components have been203  267 mm max.
developed, the standards of motherboards haveDTX
changed too; for example, with AGP beingAMD 2007
introduced, and more recently PCI Express.200  244 mm max.
However, the standardized size and layout ofMini-DTX
motherboard have changed much more slowly,AMD 2007
and are controlled by their own standards. The list200  170 mm max.smartModule
of components a motherboard must includeDigital-Logic
changes far more slowly than the components66  85 mm
themselves. For example, north bridge controllersUsed in embedded systems and single board
have changed many times since their introduction,computers. Requires a baseboard.
with many manufacturers bringing out their ownETX
versions, but in terms of form factor standards,Kontron
the requirement to allow for a north bridge has95  114 mm
remained fairly static for many years.Used in embedded systems and single board
Although it is a slower process, form factors docomputers. Requires a baseboard.nanoETXexpress
evolve regularly in response to changing demands.Kontron
The original PC standard (AT) was superseded in55  84 mm
1995 by the current industry standard ATX,Used in embedded systems and single board
which still dictates the size and design of thecomputers. Requires a carrier board. Also known
motherboard in most modern PCs. The latestas Nano COM Express Type 1
update to the ATX standard was released inExtended ATX (EATX)
2004. A divergent standard by chipsetUnknown
manufacturer VIA called EPIA (also known as12  13 in
ITX, and not to be confused with EPIC) is based305  330 mm
upon smaller form factors and its own standards.Used in rackmount server systems. Typically used
Differences between form factors are mostfor server-class type motherboards with dual
apparent in terms of their intended marketprocessors and too much circuitry for a standard
sector, and involve variations in size, designATX motherboard. The mounting hole pattern for
compromises and typical features. Most modernthe upper portion of the board matches ATX.
computers have very similar requirements, soLPX
form factor differences tend to be based uponUnknown
subsets and supersets of these. For example, a9  1113 in
desktop computer may require more sockets for229  279330 mm
maximal flexibility and many optional connectorsBased on a design by Western Digital, it allowed
and other features on-board, whereas asmaller cases than the AT standard, by putting
computer to be used in a multimedia system maythe expansion card slots on a Riser card. Used in
need to be optimized for heat and size, withslimline retail PCs. LPX was never standardized and
additional plug-in cards being less common. Thegenerally only used by large OEMs.
smallest motherboards may sacrifice CPU flexibilityMini-LPX
in favor of a fixed manufacturer's choice.Unknown
Comparisons89  1011 in
Tabular information203229  254279 mm
Form factorUsed in slimline retail PCs.
OriginatedPC/104
Max. sizePC/104 Consortium 1992
Typical feature-set3.8  3.6 in
(compared to ATX)Used in embedded systems
Typical CPUflexibilityAT Bus architecture adapted to vibration-tolerant
Power handlingheader connectors.
NotesPC104plus
(typical usage, Market adoption, etc)PC/104 Consortium 1997
XT3.8  3.6 in
IBM 1983Used in embedded systems.
8.5  11 inPCI Bus architecture adapted to vibration-tolerant
216  279 mmheader connectors.
Obsolete, see Industry Standard Architecture. ThePCI/104Express
IBM Personal Computer XT was the successor toPC/104 Consortium 2008
the original IBM PC, its first home computer. As3.8  3.6 in
the specifications were open, many cloneUsed in embedded systems
motherboards were produced and it became a dePCI Express architecture adapted to
facto standard.vibration-tolerant header connectors.
AT (Advanced Technology)NLX
IBM 1984Intel 1999
12  1113 in89  1013.6 in
305  279330 mm203229  254345 mm
Obsolete, see Industry Standard Architecture.A low-profile design released in 1997. It also
Created by IBM for the IBM Personal Computerincorporated a riser for expansion cards, and
AT, an Intel 80286 machine. Also known as Fullnever became popular.
AT, it was popular during the era of the IntelUTX
80386 microprocessor. Superseded by ATX.TQ-Components 2001
Baby-AT88  108 mm
IBM 1985Used in embedded systems and IPCs. Requires a
8.5  1013 inbaseboard.
216  254330 mmWTX
IBM's 1985 successor to the AT motherboard.Intel 1998
Functionally equivalent to the AT, it became14  16.75 in
popular due to its significantly smaller size.355.6  425.4 mm
ATXA large design for servers and high-end
Intel 1996workstations featuring multiple CPUs and hard
12  9.6 indrives.
305  244 mmXTX
Created by Intel in 1995. As of 2007[update], it is2005
the most popular form factor for commodity95  114 mm
motherboards. Typical size is 9.6  12 in althoughUsed in embedded systems. Requires a
some companies extend that to 10  12 in.baseboard.
SSI CEBPlease help improve this article by expanding it.
SSIFurther information might be found on the talk
12  10.5 inpage. (November 2007)
305  267 mmGraphical comparison of physical sizes
Created by the Server System InfrastructureMaximum number of PCI/AGP/PCI-e slots
(SSI) forum. Derived from the EEB and ATXATX case compatible:
specifications. This means that SSI CEBSpec.
motherboards have the same mounting holes andNumber
the same IO connector area as ATXATX
motherboards.microATX7
1996MicroATX
9.6  9.6 in4
244  244 mmFlexATX
A smaller variant of the ATX form factor (about3
25% shorter). Compatible with most ATX cases,Mini-DTX/DTX
but has fewer slots than ATX, for a smaller2
power supply unit. Very popular for desktop andMini-ITX
small form factor computers as of 2007[update].1
Mini-ATXVisual examples of different form factors
AOpen 2005Different form factors
5.9  5.9 inATX
150  150 mm(Abit KT7)mini-ITX
Mini-ATX is slightly smaller than Mini-ITX. Mini-ATX(VIA EPIA 5000AG)
motherboards were design with MoDT (Mobile onPico-ITX
Desktop Technology) which adapt mobile CPU for(VIA EPIA PX10000G)
lower power requirement, less heat generationPC/104 and EBX
and better application capability.PC/104 is an embedded computer standard which
FlexATXdefines both a form factor and computer bus. PC
Intel 1999104 is intended for embedded computing
9.0  7.5 inenvironments. Single board computers built to this
228.6  190.5 mm max.form factor are often sold by COTS vendors,
A subset of microATX developed by Intel inwhich benefits users who want a customized
1999. Allows more flexible motherboard design,rugged system, without months of design and
component positioning and shape. Can be smallerpaper work.
than regular microATX.The PC/104 form factor was standardized by the
Mini-ITXPC/104 Consortium in 1992. An IEEE standard
VIA 2001corresponding to PC/104 was drafted as IEEE
6.7  6.7 inP996.1, but never ratified.
170  170 mm max.The 5.75  8.0 in Embedded Board eXpandable
A small, highly-integrated form factor, designed(EBX) specification, which was derived from
for small devices such as thin clients and set-topAmpro's proprietary Little Board form-factor,
boxes.resulted from a collaboration between Ampro and
Nano-ITXMotorola Computer Group.
VIA 2003As compared with PC/104 modules, these larger
4.7  4.7 in(but still reasonably embeddable) SBCs tend to
120  120 mmhave everything of a full PC on them, including
Targeted at smart digital entertainment devicesapplication oriented interfaces like audio, analog, or
such as PVRs, set-top boxes, media centers anddigital I/O in many cases. Also it's much easier to
Car PCs, and thin devices.fit Pentium CPUs, whereas it's a tight squeeze (or
Pico-ITXexpensive) to do so on a PC/104 SBC. Typically,
VIA 2007EBX SBCs contain: the CPU; upgradeable RAM
100  72 mm max.subassemblies (e.g., DIMM); Flash memory for solid
Mobile-ITXstate disk; multiple USB, serial, and parallel ports;
VIA 2007onboard expansion via a PC/104 module stack;
2.953  1.772 inoff-board expansion via ISA and/or PCI buses
75  45 mm(from the PC/104 connectors); networking
BTX (Balanced Technology Extended)interface (typically Ethernet); and video (typically
Intel 2004CRT, LCD, and TV).
12.8  10.5 inMini PC
325  267 mm max.Mini PC is a PC form factor very close in size to
A standard proposed by Intel as a successor toan external CD or DVD drive.