Motherboard sizes: what you need to know

Come upgrade time, the motherboard is one of the most important components to come under scrutiny. Gamers often look at motherboard features such as CPU compatibility, amount of available expansion ports and technology support – but forget to take one vital aspect of the board into account: its physical size.

The various ATX standards

The smaller boards

Various smaller ATX form factors are available on the market, typically used for low-end or compact solutions. While some feature-rich, expensive motherboards with high-end features make use of the mATX form factors, typical boards will only feature two RAM slots; a single PCI-E 16x slot; and four to six SATA ports.

Smaller ATX board sizes include microATX, miniATX, and flexATX.

ATX

The most common standard used by motherboards today – chances are pretty high than you have an ATX sized motherboard in your PC. The size is large enough for boards with mid- to high-end features, such as two graphics card slots; four (or six) RAM slots; six or more SATA slots; and a fairly comprehensive cooler.

EATX and EEATX

Higher-end boards have slightly outgrown the ATX form factor, leading to the birth of extended and enhanced extended ATX boards.

EATX boards are typically the same width as normal ATX boards, though they are on average 86mm longer. This is to accommodate higher-end chipsets that feature 8 or more SATA ports; more comprehensive cooling solutions; and in some cases higher quality circuitry. Meanwhile EEATX is the same length as EATX, but 42mm wider than standard ATX boards. These boards often feature many PCIE ports to accommodate three or more graphics cards, or a mix of graphics cards and other add-on cards (such as SATA controllers or audio cards).

Of these various standards, the most common boards you’ll find are either mATX or ATX boards. Most mid-range offerings fall into these size specifications, and they don’t really experience compatibility issues with most cases.

ATX size scale comparison

Some people just have to be different

EVGA

The Californian-based motherboard company is known for their high-end offerings, as well as the overly-large size of some of their enthusiast-class motherboards.

The EVGA X58 Classified 4-Way SLI claimed it was an “XL-ATX motherboard”, with measurements of 343mm by 262mm to back up their XL claims. Wider and slightly longer than a standard ATX board, the X58 Classified 4-way would experience some mounting issues in mid-size ATX towers.

Gigabyte

Taiwan-based Gigabyte also has a range of “XL-ATX” motherboards which measure in at 325mm by 244mm – making them slightly wider than regular ATX boards, while staying the same length.

EVGA (again)

EVGA one-upped themselves in 2010 with the Super Record 2 (SR-2) motherboard boasting the HPTX form factor. The board features space for two LGA1366-based i7 CPUs, as well as 12 RAM slots as 7 PCI-E slots, necessitating the dimensions of 345mm by 381mm. This makes it one of the largest consumer level boards in the world – so it probably won’t fit in whichever case you plan on buying.

The EVGA Classified SR-2, it's a bit on the big side

Possible upgrade issues

So I’ve touched on this before in more detail here, but I’ll touch on cable length once again. Most modern cases have bottom-mounted PSUs – which could be particularly troublesome when it comes to plugging in the 12v CPU power cable, often located on the top left hand corner of the motherboard. Even if you have a PSU with longer-than-average cables, consider that cases built to fit E-ATX, XL-ATX and HPTX are far taller than regular cases.

There are also various limitations regarding your PC case. The first being the width of the motherboard tray. Many cases designed for ATX boards won’t be wide enough to accommodate ATX, XL-ATX and HPTX form factor boards. In addition to this, even if the case can accommodate the board, it probably doesn’t have the 8 or more PCI-E slots that these high-end boards often require.

Length can also be a potential issue in ATX cases. Often, shallow cases will have the 5.25 inch and 3.5 inch drive bays too close to properly install an E-ATX or longer motherboard. Other issues to consider are that even if the case has enough length to fit the board, it may obscure cable routing holes or other features. An example of this would be the Coolermaster ATCS 840, whose large main section can comfortably fit an E-ATX board, at the cost of losing the cable routing holes often used by the 24 pin motherboard power cable.