Oversized Mainboards: Why “E-ATX” is not E-ATX
Last week we explained what distinguishes the common mainboard standards ATX, Micro-ATX, ITX, as well as the intermediate sizes DTX and Flex-ATX. Boards larger than ATX were deliberately left out – and usually don’t adhere to any standards in the desktop market.
“Extended ATX” is an obvious term for extended ATX boards and is widely used for them, but there are two major misunderstandings here: First, “E-ATX” is not a free paraphrase, but a separate standard. On the other hand, mainboard manufacturers do not refer to their definition of the mainboard dimensions, but to the resulting case sizes when they specify a mainboard with “Format: E-ATX”. A circuit board larger than ATX no longer fits in every “ATX” housing, but you have to choose the next larger format – i.e. an “E-ATX” housing. This is also true when the board is just 5mm wider instead of the +86mm specified by the E-ATX standard.
E-ATX actually describes mainboards with the I/O panel, the slot configuration and the 305 mm height of a normal ATX mainboard, which instead measure 244 mm wide and 330 mm from left to right. This is not a randomly chosen number: “full length” cards according to the ISA or PCI standard are just as long; every ATX case should actually offer that much free space in its lower half. E-ATX uses the same space at full height for dual CPU systems – that’s the original ulterior motive. Today’s large workstation and server boards, including the Asus WS C621E Sage we used as a video example for E-ATX width, rely on SSI-EEB: A standard with an identical footprint, with slight variations in the ones used attachment points and additional component placement requirements.
Most E-ATX case-requiring desktop mainboards, on the other hand, have a maximum width of 267 mm of the next smaller server standard SSI-CEB instead of 330 mm. However, due to a lack of compliance with the placement regulations that are unfavorable for high-end OC boards, they may not be labeled as such, and anyway there are no desktop cases offered as SSI-CEB-compatible. So even with these boards there is always “Format: E-ATX” in the instructions, because only such housings guarantee compatibility – just like with widths between 244 mm, which exist in quarter-inch increments and are freely chosen by the mainboard manufacturers from ATX and the 267 mm from SSI-CEB.
The genuine E-ATX mainboards, which have been out of production for a long time, should not be confused with circuit boards that are more or less ATX-wide but have a greater height. Under the never standardized designation “XL-ATX” (sometimes also “Ultra-ATX”), luxury boards in various sizes were released in the late socket 775, during the -1366 and up to the -2011 era, which had up to three additional slot positions compared to ATX.
Reference-www.pcgames.de