page_title: ATX
section_title: SFX
hierarchical_section_title: ATX / Power supply / ATX power supply derivatives / SFX
caption_attribution_description: English: SFX PC Power Supply
context_page_description: ATX is a motherboard and power supply configuration specification developed by Intel in 1995 to improve on previous de facto standards like the AT design. It was the first major change in desktop computer enclosure, motherboard and power supply design in many years, improving standardization and interchangeability of parts. The specification defines the dimensions; the mounting points; the I/O panel; and the power and connector interfaces among a computer case, a motherboard, and a power supply.
  ATX is the most common motherboard design. Other standards for smaller boards usually keep the basic rear layout but reduce the size of the board and the number of expansion slots. Dimensions of a full-size ATX board are 12 × 9.6 in, which allows many ATX chassis to accept microATX boards. The ATX specifications were released by Intel in 1995 and have been revised numerous times since. The most recent ATX motherboard specification is version 2.2. The most recent ATX12V power supply unit specification is 2.4, released in April 2013. EATX is a bigger version of the ATX motherboard with 12 x 13 inch dimensions. An advantage of having an EATX motherboard is dual socket support.
context_section_description: SFX is merely a design for a small form factor (SFF) power supply casing, with the power specifications almost identical to ATX. Thus, an SFX power supply is mostly pin-compatible with the ATX power supply as the main difference is its reduced dimensions; the only electrical difference is that the SFX specifications do not require the −5 V rail. Since −5 V is required only by some ISA-bus expansion cards, this is not an issue with modern hardware and decreases productions costs. As a result, ATX pin 20, which carried −5 V, is absent in current power supplies; it was optional in ATX and ATX12V version 1.2 and deleted as of ATX version 1.3.
  SFX has dimensions of 125 × 63.5 × 100 mm (width × height × depth), with a 60 mm fan, compared with the standard ATX dimensions of 150 × 86 × 140 mm. Optional 80 or 40 mm fan replacement increases or decreases the height of an SFX unit.
  Some manufacturers and retailers incorrectly market SFX power supplies as µATX or MicroATX power supplies. 
  Besides, some manufacturers make SFX-L dimensions of 125 × 63.5 × 130 mm to accommodate 120 mm fan.
caption: An SFX power supply unit
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