Mini ATX
Mini ATX or Mini-ATX is a generic name used by motherboard manufacturers to describe a small motherboard.

A common one is the  size developed by AOpen Inc. This Mini-ATX definition is slightly smaller than the Mini-ITX  size. 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 definitions
Another definition of Mini-ATX is Intel's . This was at one time specified within the ATX specification but was later removed after the adoption of microATX.

Features

Size

With dimensions of , 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

Motherboard form factors