What is FlexATX Motherboard? (Explained)

What is FlexATX Motherboard?

FlexATX motherboard refers to a specific type of form factor which is an extension of and is built according to the Micro ATX specification.

From the design perspective, this form factor comes with similar mounting holes as the Micro ATX boards which technically makes it backwards compatible with it and ATX as well since it has the same I/O specifications as it.


  • Designed and launched in 1999, the FlexATX is a form factor that is derived from ATX but is an expansion of the specifications of the Micro ATX boards. It typically follows the CNR architecture of Intel.
  • The FlexATX motherboards are much smaller in size measuring just 9 inches by 7.5 inches which reduces the cost of manufacture and allows it to be used in smaller cases.
  • These motherboards typically cannot support more than three expansion slots as opposed to four such slots in the Micro ATX motherboard and it also does not support using any cards on it as well.
  • The term FlexATX also signifies the form factor of the Power Supply Units that can be used in smaller cases or in low-height rackmount servers.
  • The design specifications related to the mounting holes and I/O plate system makes these boards backwards compatible with ATX and Micro ATX boards.

Understanding FlexATX Motherboard

Understanding FlexATX Motherboard

Typically FlexATX is the form factor of motherboards and a spec that is derived from the ATX standard.

Developed and released by Intel in 1999, this particular specification is ideally a supplement of the specs of the Micro ATX motherboards.

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Designed on the basis of the CNR or Communications and Networking Riser architecture of Intel, this particular form factor uses the similar input-output specification or plate system as the ATX motherboards.

This smaller size of the motherboard does not allow using more than three expansion slots in it. Therefore, it allows expansion only through Universal Serial Bus or USB and IEEE-1394 or FireWire ports.

Also, the Flex architecture comes with the same type of mounting holes for the motherboard as the Micro ATX boards.

The specific features that distinguish the Flex motherboards from other ATX motherboards are:

  • Its smaller size of 9 inches × 7.5 inches or 229 mm by 191 mm
  • Its  backwards compatibility to ATX and Micro ATX boards due to similar mounting holes and I/O specs and
  • Its three expansion slots support.

FlexATX does not only refer to the small form factor of the motherboard but also the standard of the Power Supply Unit related to it.

These PSUs are usually smaller in size than any regular ATX PSU and are typically used in small form factor cases.

However, these PSUs are no mean performer because they have enough power output and robust connectors.

Depending on their designs, these power supply units can be used to run both low power and high power systems that are used for compact and versatile computing applications.

FlexATX Motherboard Dimension

What is FlexATX Motherboard

The dimension of the FlexATX motherboard is 9 inches by 7.5 inches or 229 mm × 191 mm.

The Form Factor

The FlexATX form factor is considered to be the natural development of that of the Micro ATX of Intel but with a few improvements made in it which typically addresses the necessities of the motherboard only and not of the whole system. The form factor uses the CNR architecture of Intel.

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The width of the FlexATX board is 229 mm while the depth is 191 mm.

The smaller size allows using motherboards of 9 inches x 7.5 inches which reduces the overall cost of it and also enables creating smaller system designs.

As said earlier, it is the form factor of the FlexATX that makes it backwards compatible with Micro ATX as well as the ATX specifications both.

This is also because both these types of form factors have the same mounting holes for the motherboard.

Therefore, the form factor of Flex eliminates the need to retool the current chassis of its predecessors.

What Are FlexATX PSUs?

FlexATX PSUs or Power Supply Units supply power, just as any other PSU but are slightly smaller in size in comparison to the regular ATX PSUs.

Therefore, these units are typically used in smaller chassis that house Mini ITX or FlexATX boards. It can also be used in rackmount servers with lower height such as 1U racks.

Ideally, the ATXFlex PSUs come with low power but there are a few models that come with higher power density such as that of SilverStone FX350-G.

These high power PSUs are usually super compact in design but are able to provide power output of up to 350 watts while maintaining a standard temperature threshold.

However, the smaller size of these power supply units does not allow installing a larger fan in these units and therefore a silent operation should not be expected from them.

Though a few models mention about the minimum noise output of say, 20 dB(A), there is no mention about the maximum noise output for many.

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Moreover, the cables provided with the FlexATX PSUs are also low both in power and amount because these are typically designed for use in smaller and low-power hungry machines used for special purposes and not in gaming or server computers.

FlexATX Vs Micro ATX

  • FlexATX is slightly smaller in size than a Micro ATX board being in between micro and ATX with a maximum width and depth of 229 mm and 191 mm respectively as opposed to 244 mm of both in Micro ATX boards
  • FlexATX does not use cards but Micro ATX does
  • FlexATX cannot have more than three expansion slots but Micro ATX boards can have up to four of these slots and
  • A FlexATX board can fit in a Micro ATX case but the latter cannot fit in a FlexATX case.


The FlexATX motherboards may be smaller in size but are pretty useful for implementing them in smaller and low power devices.

It is different from the Micro ATX motherboards but is not meaner in any way.

Since these can fit in a small chassis, a more compact system can be designed by the manufacturers.

About Taylor Swift

Taylor SwiftTaylor Swift, a UOPEOPLE graduate is a freelance technology writer with in-depth knowledge about computers. She has an understanding of hardware and technology gained through over 10 years of experience. Follow Her at Linkedin