The Big Form Factor Guide - ITX

The ITX family of standards were created and are primarily used by VIA. VIA's processors have historically lagged behind in performance, and so VIA have differentiated their products by offering lower-power chips, special security-related features, and uncommonly small form factors. Intel has produced some products that meet the Mini-ITX standard, yet often refers to them as microATX. A handful of Mini-ITX motherboards using AMD Geode processors are also available for embedded use.


Illustration of ITX relative to other standards

Just barely smaller than FlexATX, the original ITX standard never gained any traction in the marketplace. It was first shown as part of a reference design for an "Information PC", but was never taken up by third-party manufacturers. Its smaller derivatives would prove to be more successful.

Because this standard basically never made it into commercial production, very little information is available about it. We have had to fill in the gaps with some educated guesses.

ITX preserved nearly complete compatibility with ATX, including case mounting hole locations and the power supply connector. An ITX motherboard could be dropped directly into any case that supported microATX (the bottom-most pair of mounting holes are both required by microATX; one is optional and the other left out in regular ATX).

Maximum slots: Probably 3
Width: 215 mm (8.46 in)
Depth: 191 mm (7.5 in)
Mounting holes: Probably 6
Introduced: 2001
Link: Unavailable


Illustration of Mini-ITX relative to other standards

Once the smallest form factor around (until the launch of its smaller brethren), Mini-ITX is intended to be substantially smaller without giving up too much ATX compatibility. A Mini-ITX motherboard can be substituted directly into an ATX system with no other modifications, assuming the board has enough expansion slots to accomodate whatever expansion cards are to be used.

Like ITX, Mini-ITX sought to maintain almost complete compatibility of Mini-ITX motherboards with ATX hardware. The four mounting holes used by Mini-ITX are all mandatory in the ATX standard.

Although the Mini-ITX standard only has room for a single expansion slot on the motherboard, Mini-ITX motherboards are commonly sold with riser cards meant to alleviate the problem. These cards typically have two expansion slots and place installed expansion cards parallel to the motherboard. This has the further advantage of reducing height.

Maximum slots: 1
Width: 170 mm (6.7 in)
Depth: 170 mm (6.7 in)
Mounting holes: 4
Introduced: 2001
Link: Mini-ITX standard


Illustration of Nano-ITX relative to other standards

Even smaller than Mini-ITX, Nano-ITX boards typically eliminate "legacy" ports. They have room for a single Mini PCI slot, but no full-size PCI (or similar) slots. Nano-ITX introduced a smaller 12-pin power connector, making it incompatible with ATX power supplies.

Maximum slots: 1
Width: 120 mm (4.7 in)
Depth: 120 mm (4.7 in)
Mounting holes: 4
Introduced: 2003
Link: Unavailable


Illustration of Pico-ITX relative to other standards

Smaller still, Pico-ITX motherboards are slightly larger than a standard deck of playing cards. These boards have no expansion slots, and even have to relegate many standard ports (including USB) to motherboard headers that cables can be attached to. Pico-ITX uses the smaller Nano-ITX power connector.

Maximum slots: 0
Width: 100 mm (3.9 in)
Depth: 72 mm (2.8 in)
Mounting holes: 4
Introduced: 2007
Link: Pico-ITX standard


Illustration of Mobile-ITX relative to other standards

First demonstrated in 2008 and probably not available in volume until 2009 or later, Mobile-ITX is the single smallest form factor to implement a fully-functional x86 architecture. A Mobile-ITX motherboard fits comfortably on a typical business card. It is expected that once these products are brought to market, they will be targeted toward cellular phone applications.

Maximum slots: 0
Width: 75 mm (2.95 in)
Depth: 45 mm (1.77 in)
Mounting holes: 4
Introduced: 2008
Link: Unavailable