Mini-ITX is a 17 × 17 cm (6.7 × 6.7 in) motherboard, developed by VIA Technologies in 2001. They are commonly used in small-configured computer systems. Originally, they were a niche product, designed for fan-less cooling with a low power consumption architecture, which made them useful for home theater PC systems, where fan noise can detract from the cinema experience. The four mounting holes in a Mini-ITX board line up with four of the holes in ATX-specification motherboards, and the locations of the backplate and expansion slot are the same (though one of the holes used was optional in earlier versions of the ATX spec). Mini-ITX boards can therefore often be used in cases designed for ATX, micro-ATX and other ATX variants if desired.
The design provides one expansion slot. Earlier motherboards conventionally have a standard 33 MHz 5V 32-bit PCI slot. Many older case designs use riser cards and some even have two-slot riser cards, although the two-slot riser cards are not compatible with all boards. Some boards based around non-x86 processors have a 3.3V PCI slot, and the Mini-ITX 2.0 (2008) boards have a PCI-Express ×16 slot; these boards are not compatible with the standard PCI riser cards supplied with older ITX cases.