Mini-STX

Mini-STX (aka Mini Socket Technology EXtended, Intel 5x5) is a computer motherboard form factor that supports upgradable processors. The motherboard size is 147×140 mm, which is between Intel's NUC (next unit of computing) motherboards and Mini-ITX boards that are popular in small form-factor builds.

ASRock extended it by two inches to add an MXM slot creating Micro-STX.

Comparisons with NUC

When compared with NUC, the Mini-STX form factor:

• Has 3/2 the motherboard area of a NUC.
• Has processor sockets, allowing for users to upgrade or replace processors.
• Offers the possibility of dedicated GPUs via MXM (on some models produced by ASRock).
• May have more I/O options due to the larger space available on the back of the board.

Comparisons with Mini-ITX

When compared with Mini-ITX, the Mini-STX form factor:

• Has a motherboard area 3/4 the size of Mini-ITX.
• Is usually limited to SO-DIMMs, rather than full-size DIMMs.
• Lacks a full-size PCIe expansion slot, limiting users to MXM GPUs or less powerful, integrated GPUs and APUs.
• May have less I/O options due to the reduced space available on the back of the board.
• May use a 2-in-1 SATA+power cable instead of separate SATA and power cables.

References

• http://www.pcworld.com/article/2975764/components/intel-unveils-ultra-tiny-fully-upgradable-5x5-mini-pc-motherboards.html
• http://www.intel.com/content/www/us/en/technology-provider/products-and-solutions/desktop/mini-stx-for-mini-pcs.html
• http://www.asrock.com/mb/Intel/H110M-STX/
• https://www.asrock.com/nettop/AMD/DeskMini%20A300%20Series/ (AMD AM4)
• https://www.asus.com/Motherboards/H110S1/
• https://www.asus.com/Motherboards/H110S2/
• https://www.asus.com/Motherboards/Q170S1/
• https://www.gigabyte.com/Motherboard/GA-H110MSTX-HD3-rev-10#ov