MOTHERBOARD FORM FACTORS




In computing, a form factor specifies the physical dimensions of motherboard.

A PC motherboard is the main circuit board within a typical desktop computer, laptop or server. Its main functions are as follows:

* to serve as a central backbone to which all other modular parts such as CPU, RAM, and hard drives can be attached as required to create a modern computer;
* to accept (on many motherboards) different components (in particular CPU and expansion cards) for the purposes of customization;
* to distribute power to PC components;
* to electronically co-ordinate and interface the operation of the components.

Tabular information

Form factor Originated Max. size Notes
(typical usage, Market adoption, etc.)
XT IBM 1983 8.5 × 11 in
216 × 279 mm
Obsolete, see Industry Standard Architecture. The IBM Personal Computer XT was the successor to the original IBM PC, its first home computer. As the specifications were open, many clone motherboards were produced and it became a de facto standard.
AT (Advanced Technology) IBM 1984 12 × 11–13 in
305 × 279–330 mm
Obsolete, see Industry Standard Architecture. Created by IBM for the IBM Personal Computer/AT, an Intel 80286 machine. Also known as Full AT, it was popular during the era of the Intel 80386 microprocessor. Superseded by ATX.
Baby-AT IBM 1985 8.5 × 10–13 in
216 × 254–330 mm
IBM’s 1985 successor to the AT motherboard. Functionally equivalent to the AT, it became popular due to its significantly smaller size.
ATX Intel 1996 12 × 9.6 in
305 × 244 mm
Created by Intel in 1995. As of 2007[update], it is the most popular form factor for commodity motherboards. Typical size is 9.6 × 12 in although some companies extend that to 10 × 12 in.
SSI CEB SSI 12 × 10.5 in
305 × 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.
SSI EEB SSI 12 × 13 in
305 × 330 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.
SSI MEB SSI 16.2 × 13 in
411 × 330 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.
microATX 1996 9.6 × 9.6 in
244 × 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[update].
Mini-ATX AOpen 2005 5.9 × 5.9 in
150 × 150 mm
Mini-ATX is slightly smaller than Micro-ITX. Mini-ATX motherboards were design with MoDT (Mobile on Desktop Technology) which adapt mobile CPU for lower power requirement, less heat generation and better application capability.
FlexATX Intel 1999 9.0 × 7.5 in
228.6 × 190.5 mm max.
A subset of microATX developed by Intel in 1999. Allows more flexible motherboard design, component positioning and shape. Can be smaller than regular microATX.
Mini-ITX VIA 2001 6.7 × 6.7 in
170 × 170 mm max.
A small, highly-integrated form factor, designed for small devices such as thin clients and set-top boxes.
Nano-ITX VIA 2003 4.7 × 4.7 in
120 × 120 mm
Targeted at smart digital entertainment devices such as PVRs, set-top boxes, media centers and Car PCs, and thin devices.
Pico-ITX VIA 2007 100 × 72 mm max.
Mobile-ITX VIA 2007 2.953 × 1.772 in
75 × 45 mm
BTX (Balanced Technology Extended) Intel 2004 12.8 × 10.5 in
325 × 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 RAM slots and the PCI slots are parallel to each other.Processor is placed closest to the fan. May contain a CNR board.
MicroBTX (or uBTX) Intel 2004 10.4 × 10.5 in
264 × 267 mm max.
PicoBTX Intel 2004 8.0 × 10.5 in
203 × 267 mm max.
DTX AMD 2007 200 × 244 mm max.
Mini-DTX AMD 2007 200 × 170 mm max.
smartModule Digital-Logic 66 × 85 mm Used in embedded systems and single board computers. Requires a baseboard.
ETX Kontron 95 × 114 mm Used in embedded systems and single board computers. Requires a baseboard.
COM Express Basic PICMG 95 × 125 mm Used in embedded systems and single board computers. Requires a carrier board.
COM Express Compact PICMG 95 × 95 mm Used in embedded systems and single board computers. Requires a carrier board.
nanoETXexpress Kontron 55 × 84 mm Used in embedded systems and single board computers. Requires a carrier board. Also known as COM Express Ultra and adheres to pin-outs Type 1 or Type 10[1]
CoreExpress SFF-SIG 58 × 65 mm Used in embedded systems and single board computers. Requires a carrier board.
Extended ATX (EATX) Unknown 12 × 13 in
305 × 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.
LPX Unknown 9 × 11–13 in
229 × 279–330 mm
Based on a design by Western Digital, it allowed smaller cases than the AT standard, by putting the expansion card slots on a Riser card.[2] Used in slimline retail PCs. LPX was never standardized and generally only used by large OEMs.
Mini-LPX Unknown 8–9 × 10–11 in
203–229 × 254–279 mm
Used in slimline retail PCs.
PC/104™ PC/104 Consortium 1992 3.8 × 3.6 in Used in embedded systems. AT Bus (ISA) architecture adapted to vibration-tolerant header connectors.
PC/104-Plus™ PC/104 Consortium 1997 3.8 × 3.6 in Used in embedded systems. PCI Bus architecture adapted to vibration-tolerant header connectors.
PCI/104-Express™ PC/104 Consortium 2008 3.8 × 3.6 in Used in embedded systems.
PCI Express architecture adapted to vibration-tolerant header connectors.
PCIe/104™ PC/104 Consortium 2008 3.8 × 3.6 in Used in embedded systems.
PCI/104-Express without the legacy PCI bus.
NLX Intel 1999 8–9 × 10–13.6 in
203–229 × 254–345 mm
A low-profile design released in 1997. It also incorporated a riser for expansion cards, and never became popular.
UTX TQ-Components 2001 88 × 108 mm Used in embedded systems and IPCs. Requires a baseboard.
WTX Intel 1998 14 × 16.75 in
355.6 × 425.4 mm
A large design for servers and high-end workstations featuring multiple CPUs and hard drives.
HPTX EVGA 2008 13.6 × 15 in
345.44 × 381 mm
A large design by EVGA, it has dual-CPU (Intel Xeon 55xx and 56xx) support, Four-Way nVIDIA SLI or ATi Crossfire support, up to 8 3.5in HDD support, and supports 48GB of RAM. Cases need to have at least 9 expansion slots and the required dimensions to be compatible.
XTX 2005 95 × 114 mm Used in embedded systems. Requires a baseboard.

Maximum number of PCI/AGP/PCI-e slots

ATX case compatible:

Specification Number
HPTX 9
ATX 7
MicroATX 4
FlexATX 3
DTX 2
Mini-DTX/DTX 2
Mini-ITX 1
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