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XT (IBM)
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. 216 × 279 mm -
AT (Advanced Technology) (IBM)
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 Superseded by ATX. 305 × 279–330 mm -
Baby-AT (IBM)
IBM's 1985 successor to the AT motherboard. Functionally equivalent to the AT, it became popular due to its significantly smaller size. 216 × 254–330 mm -
PC/104 (PC/104 Consortium)
Used in embedded systems. AT Bus (ISA) architecture adapted to vibration-tolerant header connectors. 97 × 91 mm -
SSI CEB (SSI)
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. 305 × 267 mm -
ATX (Intel)
Created by Intel in 1995. As of 2017, 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. 305 × 244 mm -
SSI EEB (SSI)
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, but SSI EEB motherboards do not. 305 × 330 mm -
LPX (Western Digital)
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. Used in slimline retail PCs. LPX was never standardized and generally only used by large OEMs. 229 × 279–330 mm -
Mini-LPX (Western Digital)
Used in slimline retail PCs. 203–229 × 254–279 mm -
SSI MEB (SSI)
Created by the Server System Infrastructure (SSI) forum. Derived from the EEB and ATX specifications. 411 × 330 mm -
microATX (Intel)
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 2017. 244 × 244 mm -
PC/104-Plus (PC/104 Consortium)
Used in embedded systems. PCI Bus architecture adapted to vibration-tolerant header connectors. 97 × 91 mm -
Extended ATX (Supermicro-Asus)
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. 305 × 330 mm -
WTX (Intel)
A large design for servers and high-end workstations featuring multiple CPUs and hard drives. -
SWTX (Supermicro)
A proprietary design for servers and high-end workstations featuring multiple CPUs. 418 × 330 mm -
NLX (Intel)
A low-profile design released in 1997. It also incorporated a riser for expansion cards, and never became popular. 203–229 × 254–345 mm -
FlexATX (Intel)
A subset of microATX developed by Intel in 1999. Allows more flexible motherboard design, component positioning and shape. Can be smaller than regular microATX. 228.6 × 190.5 mm -
Mini-ITX (VIA)
A small, highly integrated form factor, designed for small devices such as thin clients and set-top boxes. 170 × 170 mm max -
UTX (TQ-Components)
Used in embedded systems and IPCs. Requires a baseboard. 88 × 108 mm -
Nano-ITX (VIA)
Targeted at smart digital entertainment devices such as PVRs, set-top boxes, media centers and Car PCs, and thin devices. 120 × 120 mm -
BTX - Balanced Technology Extended (Intel)
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. 325 × 267 mm -
MicroBTX (Intel)
MicroBTX (also called uBTX) is a computer motherboard form factor. A microBTX is 10.4 × 10.5 in (264 × 267 mm) and can support up to four expansion slots. 264 × 267 mm -
COM Express Mini (PICMG)
Used in embedded systems and single-board computers. Requires a carrier board. Adheres to pin-out Type 10. 55 × 84 mm -
XTX (Ampro-Congatec)
Used in embedded systems. Requires a base. 95 × 114 mm -
Mac Mini (Apple)
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COM Express Compact (PICMG)
Used in embedded systems and single-board computers. Requires a carrier board. 95 × 95 mm -
COM Express Basic (PICMG)
Used in embedded systems and single-board computers. Requires a carrier board. 95 × 125 mm -
Mini-ATX (AOpen)
Mini-ATX is considerably smaller than Micro-ATX. Mini-ATX motherboards were designed with MoDT (Mobile on Desktop Technology) which adapt mobile CPUs for lower power requirement, less heat generation and better application capability. 150 × 150 mm -
DTX (AMD)
200 × 244 mm max -
Pico-ITX (VIA)
100 × 72 mm max -
Mobile-ITX (VIA)
75 × 45 mm -
PCI/104-Express (PC/104 Consortium)
Used in embedded systems.
PCI Express architecture adapted to vibration-tolerant header connectors. 97 × 91 mm -
HPTX (EVGA)
A large design by EVGA currently featured on two motherboards; the eVGA SR2 and SRX. Intended for use with multiple CPUs. Cases require 9 expansion slots to contain this form-factor. 345 × 381 mm -
CoreExpress (SFF-SIG)
Used in embedded systems and single-board computers. Requires a carrier board. 58 × 65 mm -
Neo-ITX (VIA)
Used in the VIA Android PC 170 × 85 × 35 mm -
NUC - Next Unit of Computing (Intel)
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Mini-STX (Intel)
Smaller than Mini-ITX, but bigger than the NUC, this board is used in small form factor computers, using a socketed intel core processor and SO-DIMMS. 147 × 140 mm -
COM-HPC Size D (PICMG)
Used in embedded systems. Requires a carrier board. Typically used for COM-HPC Server Type modules with 4x full size DIMM memory sockets. 160 × 160 mm -
COM-HPC Size A (PICMG)
Used in embedded systems. Requires a carrier board. Typically used for COM-HPC Client Type modules. 95 × 120 mm -
COM-HPC Size B (PICMG)
Used in embedded systems. Requires a carrier board. Typically used for COM-HPC Client Type modules. 120 × 120 mm -
COM-HPC Size C (PICMG)
Used in embedded systems. Requires a carrier board. Typically used for COM-HPC Client Type modules with multiple SODIMM memory sockets. 160 × 120 mm -
COM-HPC Size E (PICMG)
Used in embedded systems. Requires a carrier board. Typically used for COM-HPC Server Type modules with 8x full size DIMM memory sockets. 200 × 160 mm