Mini ATX
Mini ATX or Mini-ATX is a generic name that may be used by motherboard manufacturers to describe a small motherboard, and has been used by AOpen in reference to a motherboard design with dimensions 15 × 15 cm (5.9 × 5.9 in).

Mini-ATX motherboards were designed with MoDT (Mobile on Desktop Technology) which adapt mobile CPUs for lower power requirements and less heat generation, which may be beneficial for home theater PCs (HTPC), in-car PCs, or industrial use.
Alternative Definition
The term miniATX was originally used in (now obsolete versions of) Intel's ATX specification, and denoted motherboards with dimensions of 284 x 208 mm (11.2 x 8.2 in.), before being abandoned in v2.1 in favor of the microATX specification. The two terms refer to different specifications and should not be conflated.
Features
Size
With dimensions of 15 × 15 cm (5.9 × 5.9 in), an AOpen-spec Mini-ATX motherboard can be placed into a single DIN space for standardized application conditions such as a car, rack mount, tower case, wall mount, etc. which may be impossible for the larger Mini-ITX form factor. The smaller form factor Nano-ITX motherboard lacks a CPU socket module which limits its flexibility for different applications.
Noise
Due to a mobile CPU having lower power requirements, there is less heat generated by the CPU and internal components, and the thermal design is simplified. With its passive cooling design, it is typically noiseless and the manufacturing costs and overall operating power requirements are lower relative to active cooling designs.
Stability
Mini-ATX motherboards use surface-mount technology, solid state capacitors and 8 layers PCB design to maximize reliability.
Flexibility
The DC-to-DC converter solution design removes the power supply unit from a Mini-ATX case. This reduces the system size and an external power supply unit brings more flexibility when deploying system.
References
External links
- PCtechguide on the ATX form factor: https://www.pctechguide.com/motherboards/atx-form-factor
- Other form factors information from C&T: http://www.codesandtutorials.com/hardware/computerfundamentals/motherboard-types-form_factor.php