Eatx spec

Eatx spec DEFAULT

1USB BIOS Flashback™

28 x USB 3.1 Gen 1 Ports

3Intel® Gb LAN

4USB 3.1 Gen 2
Type A/C Ports

58 CH Audio with
DTS Support

64 x PCIe 3.0 (GEN3)
2-Way/3-Way SLI & CFX Support

Crystal Sound 3
  • Power pre-regulator
  • Internal audio ampilier
  • De-pop circuit
  • Separate layer for left/right track
  • Premium Japan-made audio capacitors

8DIGI+ Power Control

9DDR4 3600(O.C.) Support

10AMD SocketTR4

11M.2 Slot

12USB 3.1 Gen 2 Front-Panel Connector

13ASUS SafeSlot

14U.2 Port

156 x SATA 6Gb/s

16M.2 Heatsink


ASUS Prime X399-A is the EATX motherboard that's been expertly engineered for professional content creators and power users who work hard by day and play harder by night. This powerful, innovative board puts a friendly face on advanced enthusiast controls, enabling you to maximize performance, cooling and personalization with ease. So, if you live to create, explore, and to push the boundaries, look no further than the Prime X399-A.

Ready for 2nd Gen AMD Ryzen Threadripper

The Prime X399-A Cooling Kit contains an SOC heatsink and a fan bracket, designed to cool vital motherboard power delivery areas to enhance the overclocking potential of 2nd Gen Threadripper WX Series Processors.

Tune it your way

5-Way Optimization

One-click overclock and cooling, done!

One click takes care of all that complex tuning. ASUS 5-Way Optimization makes your PC smart. It dynamically optimizes essential aspects of the system, providing overclocking and cooling profiles that are tailored for your rig.

An automated tuning utility that optimizes overclocking and cooling profiles for your unique system configuration.

Fans stay whisper-quiet for everyday computing, and deliver optimal airflow when the system is crunching through CPU or GPU-intensive tasks.

All-new stress test that allows users to optimize and overclock for CPU or memory-centric workloads.

Overclock CPU

CPU :  Ryzen™ Threadripper™ 1950X | Motherboard: PRIME X399-A | DRAM: G.Skill F4-3866C18Q-16GTZ | PSU: Cooler Master-RS850-AFBA-G1 | Water-cooling : Corsair H115i

CPU performance boost

Unleash your PC's full performance with the ASUS AI Suite 3 utility. A TurboV Processing Unit (TPU) is the intelligence behind our automated system-tuning utility, offering the ability to fine-tune voltages, monitor system stats, and adjust overclock parameters for optimal performance.

All-round energy efficiency

With the Energy Processing Unit (EPU) you'll enjoy system-wide power savings. The EPU automatically optimizes power consumption and maximizes savings with Away mode.

Flexible cooling controls for air or liquid

With Prime X399-A you have comprehensive control over fans, water pumps and even all-in-one (AIO) coolers, via either Fan Expert 4 or our award-winning UEFI. Whether you're cooling with air or water, Auto-Tuning mode intelligently configures all parameters with a single click. There's also an Extreme Quiet mode, which reduces all fan speeds to below the default minimum — keeping your system whisper-quiet when performing light tasks.

Precise digital power control

Digi+ delivers real-time control over voltage droop, switching frequency and power -efficiency settings, allowing you to fine-tune CPU voltage regulation for ultimate stability and performance.

App specific optimization for professionals and gamers

Whether you're a professional designer or hardcore gamer, you'll feel the benefit of the ASUS-exclusive Turbo App every day. This intuitive tool allows you to define CPU overclocking, apply fan profiles, prioritize network data and optimize audio settings at app level, meaning your Prime X399-A system is perfectly optimized for what you're doing.

Cooler by design

Prime X399-A features the most comprehensive cooling controls ever, configurable via Fan Xpert 4 or the UEFI BIOS:

Each header can be set to monitor and react to three thermal sensors, and via Fan Xpert 4 you can even assign a sensor to monitor the temperature of supported ASUS graphics cards, for optimal cooling during GPU or CPU-intensive workloads.

A dedicated header that supplies over 3A for high-performance PWM or DC water pumps, plus a second dedicated header for AIOs.

A built-in fan attached to the main heatsink array that helps cool the CPU VRM.

Every onboard header supports auto-detection of PWM or DC fans.

Includes three additional DC or PWM fan headers, plus three thermal-probe headers.

A dedicated integrated circuit that protects each fan header from over-temperature and over-current.

Media-acclaimed UEFI BIOS

The smoothest, slickest mouse-controlled graphical BIOS has been improved to make it even more appealing. Whether you're a PC novice or a seasoned overclocker, the EZ and Advanced Modes help you find your way, quickly and easily.

EZ Tuning Wizard Quickly apply a CPU overclock to improve system performance

My Favorites Quickly discover tuning options and add preferred tools to the list.

Learn more

EZ Mode

Intuitive graphical fan control: Fine-tune individual fans simply by dragging a curve with the mouse.

EZ XMP: Improve your DRAM performance with a click.

SATA Information: Displays SATA port details so you can easily recognize drives.

Fast Clock Adjustment: Use mouse controls to change the time and date.

Advanced Mode

GPU POST: Provides recommendations for multi-VGA configurations and detailed information for select ASUS graphics cards.

Secure Erase: Restores your SSDs to factory-fresh condition.

Last Modified Log: Track last change and save preferred profiles onto a USB drive.

SATA Port Renaming: Rename SATA ports for easy identification.

Make your memory go faster

Prime X399-A is engineered to support quad-channel memory kits rated up to a staggering DDR4 3600MHz, allowing you to get the best performance from the X399 platform. We've worked with all major DDR4 memory vendors to help ensure compatibility, so you're assured the best compatibility.

OC Design – ASUS Pro Clock Technology

A dedicated base-clock generator that extends CPU and memory overclocking margins. This custom solution works in tandem with the TPU to enhance voltage and base-clock overclocking control, providing the flexibility to extract every ounce of performance from Ryzen™ Threadripper™ processors.

BCLK Range

*BCLK overclocking range will vary according to CPU capabilities, cooling, motherboard support and tuning options.
CPU : Ryzen™ Threadripper™ 1950X | Motherboard: PRIME X399-A | DRAM: G.Skill F4-3866C18Q-16GTZ | PSU: Cooler Master-RS850-AFBA-G1 | Water-cooling : Corsair H115i

Learn more

Connect everything, ultra-fast


Speed up with onboard M.2 up to 32Gbps

With x4 PCI Express 3.0/2.0 bandwidth, M.2 supports up to 32Gbps data-transfer speeds. It is the perfect choice for an operating system or application drive, providing fast access to data.

M.2 heatsink

Keep your SSD cooler

Prime X399-A has an ultra-efficient heatsink to reduce M.2 SSD temperatures by up to 20°C — and that means optimal storage performance and improved SSD longevity.

U.2 connector

Join the NVMe revolution

The revolutionary specification that lets your SSDs scream at top speed. Just attach your chosen drive to with plug-and-play ease to experience data-transfer speeds of up to 32Gbps — and free up a PCIe slot for another expansion card.

USB 3.1 Gen 2 front-panel connector

Future-proof connectivity

Prime X399-A's front panel USB 3.1 connector is ready for next-gen PC cases and devices.

USB 3.1 Gen 2 Type-A & Type-C

Ultimate-speed 10Gbps with USB 3.1 onboard

With backward-compatible USB 3.1 Gen 2 Type-A™ and reversible USB 3.1 Gen 2 Type-C™ ports, you'll experience ultimate connection flexibility and blazing data-transfer speeds of up to 10Gbps.

Intel Ethernet

More throughput, less CPU usage

Prime X399-A features the latest Intel Ethernet. Intel's LAN has the advantage of reducing CPU overhead and offering exceptionally high TCP and UDP throughput for faster, smoother data transfer.

Lower CPU workload

High TCP & UDP throughput

Learn more


Pumped-up throughput, 2.5x higher surge tolerance

ASUS LANGuard is hardware-level networking protection that employs signal-coupling technology and premium anti-EMI surface-mounted capacitors to ensure a more reliable connection and better throughput.

Turbo LAN

Network-optimization software for customizable packet prioritization

Turbo LAN with cFosSpeed traffic-shaping technology allows you to configure application priority via an intuitive interface, and reduces network lag.

Step up to multi-GPU graphics

Multi-GPU support

With support for both NVIDIA® SLI™ and AMD CrossFireX™ 2/3-WAY configurations, Prime X399-A motherboard enables multi-GPU setups so you can harness the full power of the latest graphics technologies to drive games at 4K and beyond.


Protect your graphics card investment

SafeSlot* is the PCIe slot reinvented by ASUS and engineered to provide superior retention and shearing resistance. Manufactured in a single step using a new insert-molding process, SafeSlot integrates the slot with fortifying metal for an inherently stronger slot, which is then firmly anchored to the PCB through additional solder points.

*Patent pending

Upgrade to unrivalled audio

Outstanding audio

Realtek codec and unique design features for pristine, powerful audio

Prime X399-A utilizes a unique audio codec designed in close collaboration with Realtek — the Realtek S1220A. It also features an unprecedented 120dB signal-to-noise ratio for the stereo line-out and a 113dB SNR for the line-in, providing pristine audio quality. Additionally, a new impedance-sensing circuit automatically adjusts gain to ensure the optimal volume range for your headphones.

DTS Headphone:XTMSurround sound, to go

Immersive 3D surround-sound technology provides incredible audio experiences.

Crystal Sound 3

Flawless audio that makes you part of the game

Power pre-regulator

Reduces power-input noise to ensure consistent performance.

Audio shielding

Separates analog/digital signal domains, significantly reducing multi-lateral interference.

Separate layer for left and right tracks

Ensures minimal crosstalk between audio paths.

Integrated amplifier

Capable of driving high-impedance headphones, without rolling-off high or low frequencies.

De-pop circuit

Reduces start-up popping noise to all audio outputs.

Premium Japanese-made audio capacitors

Premium parts provide an immersive sound signature, with exceptional fidelity.

Make it your own

Exclusive 3D mount for easy installation

Make it your own

Dedicated 3D mounts on the motherboard makes fitting 3D-printed parts easy. Using the same screws as M.2 drives and standard motherboard mounting holes, you can easily add nameplates and cable covers.

M.2 fan holder A fan mount for M.2 drives to help prevent thermal throttling.

Learn more

3D-printable accessories

As system parts are visible in custom PC builds, make yours stand out from the competition with 3D-printed accessories.

Graphics card holder Prevent sag by providing support for heavy graphics cards.

2-Way SLI HB Bridge cover Clip the cover onto the SLI HB Bridge to add style to your build. Multiple form factors — EATX, ATX and mATX — are available.

Fan grill Make your cooling a little cooler.

Cable combs Keep cables organized with the multi-connector design. 3D design files are available for 24-pin, 8-pin, 8 + 6-pin, 6-pin and 4-pin PSU connectors.

Guide to start 3D printing

Download Select the 3D source files you want to download.


Personalize Adjust size or shape, add text or change other attributes.

Watch tutorial

Print Use your own printer, or visit a local vendor or ASUS store with Shapeways.


Setup Easily assemble and fit your 3D-printed parts using M.2 nuts or existing case mounts.

Watch tutorial

Ready for AMD SocketTR4 Ryzen Threadripper The ASUS Prime X399-A motherboard supports the latest 2nd Gen AMD Ryzen™ Threadripper™ and AMD Ryzen™ Threadripper™ processors. Based on the innovative Zen core architecture, the high-performance Threadripper CPUs boast up to 32 cores. AMD SocketTR4 processors feature quad-channel DDR4 memory, 64 lanes of PCI Express® 3.0 and native 5Gbps USB 3.0 for superb performance.

AMD X399 chipset The AMD X399 chipset delivers outstanding overclocking capabilities for the latest AMD SocketTR4 Ryzen™ Threadripper™ processors. It's optimized for multiple GPU configurations, including NVDIA SLI™ and AMD CrossFireX™. It also provides two 10Gbps USB 3.1 ports and eight 6Gbps SATA ports for faster data retrieval.


original atx size

ATX is a spec released by Intel in 1995 and occasionally updated since then. It stands for Advanced Technology eXtended, and it was intended to replace the older de facto AT standard established by the IBM AT, a PC released in 1984. It’s been used as the industry-wide standard since its introduction, and has thus far resisted Intel’s attempt to replace it, like the BTX form factor for motherboards in 2004 and the new ATX12VO standard for PSUs and motherboards published in 2019. The full ATX/ATX12V spec defines many aspects of both motherboards and power supplies, not just their size, but the only thing we’re concerned with today is motherboard form factor and why EATX is a bullshit term for it.

atx specification 22

case up to sizing

Note: we’re going to refer to the motherboard’s dimensions based on how they’re normally oriented in a case, so the distance from the bottom to the top is height, and from the front (of the case) to the back is width. Dimensions are written as height x width.

EATX or E-ATX stands for extended ATX, creating the unfortunate acronym Extended Advanced Technology eXtended, which sounds like a bad ad for a product you’d see on a different video website. EATX is defined as 12 inches tall by 13 inches wide, if it’s even defined at all, while a standard ATX board is 12 inches tall and 9.6 inches wide. Other companies have occasionally taken it upon themselves to complicate things, as with Supermicro’s EE-ATX, which obviously means “Enhanced Extended Advanced Technology eXtended,” and then there’s XL-ATX, a name which has been used by EVGA, Gigabyte, and MSI to describe three nearly-identical motherboard sizes. Let’s not forget BTX, or “Balanced Technology eXtended,” a standard measured 10.5”x12.8” and, although some parts of it are now laughably outdated (like the recommendation to cool the CPU using only airflow from the PSU), the additional PCB space it offered may have sidestepped this whole mess if it had been more widely adopted.

btx form factor

As a brief aside, XL-ATX -- any of the three that exist -- is essentially the “what if we made it taller, too” alternative to ATX. Making an ATX board taller allows more room for chipset cooling and PCIe slots, which are primarily useful for multi-GPU setups, which are increasingly rare. That and the increasing popularity of PSU shrouds which put a hard limit on motherboard height mean that XL-ATX is effectively dead, even though it’s still being used. It’s been supplanted by boards that increase width instead, known as “EATX,” which isn’t real and should be regarded as a fairy tale. Extra width gives more room for RAM and larger/multiple CPU sockets, which are more desirable at this point than extra GPUs.

Gigabyte, as another aside, can't even get it right. They don't know if their product is E-ATX or XL-ATX, but they've listed it as both on Amazon and on their own product page.

x299x eatx sizing

gigabyte eatx vs xl atx

Confusingly, the SSI-EEB (Server System Infrastructure Forum’s Enterprise Electronics Bay, originally known as Entry[-Level] Electronics Bay) form factor is an ATX variant that’s exactly the same dimensions as full EATX and shares most of its mounting holes. EEB is interchangeable with SSI-EEB as a name for the form factor. The original EEB spec says that “the dimensions of this E-Bay are based on the standard AT board dimensions, 12 inches x 13 inches,” and it appears that most of the mounting holes are based on the now 36-year-old form factor as well, although component layout has changed. Version 1.0 of the SSI-EEB spec is dated 1999, but the term “extended ATX” predates this. We spoke to several manufacturers while researching for this piece, and one of them remembered ASUS as the possible origin of EATX as a marketing term through their in-house brand ElanVital. We checked, and it appears that ElanVital started calling cases “EATX” that they had formerly branded “AT” sometime in 2002-2003. The lines are extremely blurred here, because AT and EEB are different names for the same size of board, as was EATX originally. Before it was ruined.

ssi eeb sizing

entry e bay requirements

The major problem with EATX is that it isn’t defined. We’ve skirted around this so far, but EATX is a blanket term slapped on any ATX board wider than 9.6 inches, not an official spec. EATX is used as a marketing term by both motherboard and case manufacturers to signify any motherboard that’s wider than 9.6 inches and therefore won’t fit in a normal ATX case, while 12”x13” SSI-EEB boards are usually referred to with a prefix like “true EATX” or “full EATX.” Because we needed more distinctions, and motherboard makers can reap what they sow, damn it.

evga x58 classified eatx

evga x58 classified 2

The SSI Forum defined multiple form factors, like the 12”x10.5” Compact Electronics Bay, and EATX is used as a generic term for that as well. This may be EVGA’s fault: as early as 2009, they were referring to the SSI-CEB X58 Classified as “EATX,” after which other companies like Gigabyte and ASUS followed suit, which has forced case manufacturers to use the phrase “EATX-compatible” to convey that they support motherboards wider than 9.6”. From EVGA’s perspective, it was necessary to have a quick way to say that a board wouldn’t fit in a normal mid-tower. Silverstone is one of the few holdouts that refuses to use EATX to mean anything other than 12”x13”.

silverstone eeb

silverstone eeb2

There isn’t an official spec for EATX, just ATX, but both EATX and SSI-EEB boards simply add an additional column of screw holes to the three that are present in normal ATX boards. You can check the numbers yourself if you want, but we’ll save you some time and confirm that normal SSI-EEB hole spacing is exactly the same as normal ATX, plus some extra. Let’s repeat that, because it’s a point of confusion even among case and motherboard manufacturers: SSI-EEB is based on ATX and uses exactly the same hole placement with some alternative and extra holes thrown in.

“Full” or “true” 13-inch EATX boards are EEB boards. EEB also has options for some extra holes around the PCIe slots and potentially a secondary CPU socket, since it’s meant for server boards.

eeb sizing holes prime

ssi eeb spec3

Note that not all of the SSI-EEB holes are required, and the ones marked with an apostrophe are alternatives to the “legacy” ATX locations to allow motherboard manufacturers more freedom in placing components. The alternate holes weren’t present in the original spec, and they do NOT line up with the ATX standard, so if a board manufacturer chooses to use any of them, it limits compatibility with ATX/EATX cases. This is why there’s so much conflicting information online about whether “EATX” and EEB are interchangeable: if a manufacturer just uses the primary ATX-compatible holes, the board will probably be referred to as EATX and everything is hunky-dory. If they use any of the alternate EEB hole placements and call the board SSI-EEB, the logical conclusion for a user trying to install the board is that EEB hole spacing is different from EATX.

Even boards that refer to themselves as E-ATX may make use of the alternate EEB hole placements: for example, EVGA’s SR-3 uses the Y’ [Y Prime] mounting hole. The SSI Forum took care to point out that motherboard manufacturers can skip any mounting holes they don’t want, but cannot add any additional ones. It’s interesting to see that as of at least 2011, the SSI-EEB spec name-drops EATX and acknowledges that it’s a common name for 12”x13” boards.

ssi eeb requirements

This problem has expanded beyond motherboards to affect the products that are related to them, like cases. Here are the ten most recent regular consumer cases we’ve reviewed, and how they describe their maximum motherboard size compatibility, verbatim:

  • Fractal Define 7: “E-ATX (max 285mm)”
  • Antec P120 Crystal: “E-ATX” [in downloadable flyer: “up to 12” x 11”]
  • Lian Li Lancool II: “E-ATX/ATX (width: under 280mm)”
  • Bitfenix Nova Mesh TG: “E-ATX up to 272mm(10.7 inch)”
  • NZXT H710: “EATX (Up to 272mm or 10.7-inches)”
  • Phanteks P400A: “E-ATX *(up to 272mm wide, cannot use rubber grommets)”
  • Lian Li O11 XL: “E-ATX (need to purchase an extension panel for EEB motherboards)”
  • Corsair 465X: “ATX”
  • Fractal Define S2 Vision: “EATX (up to 285 mm wide)”
  • Corsair 220T: “full-sized ATX”

ceb diagram

Out of those ten cases, eight of them claim to support EATX, and not a single one of them other than the O11 XL can fit the full 13in/330mm width of the EVGA SR-3. Even the XL officially requires a separately-purchased part for 13-inch wide boards to fit. We can’t get too mad at these particular case manufacturers though, because (other than Antec) they do all include specific notes about what size of EATX boards they can fit--there are “EATX” boards that are between 9.6 and 13 inches wide, like EVGA’s 10.9 inch wide X299 Dark. We can get mad about the fact that they have to include these notes at all, rather than just saying the name of a form factor. This is stupid. It actually takes more space to type out “EATX up to 11 inches” than it does to write 12”x11”.

The reason these cases aren’t compatible with wider boards isn’t consistent, either. Sometimes, cases like the Fractal Define 7 seem like they could easily support much wider boards with some minor adjustments to the rim of the motherboard tray. There are also plenty of cases that have relatively empty space in front of the motherboard tray that’s blocked by a cable management channel, like the P120 Crystal. Even if there isn’t room for a full set of SSI-EEB standoffs, it would be easy for so many cases to allow wider boards to fit and overhang at the front of the case. The elimination of optical and hard drive cages has left this area of cases a no man’s land, and wider motherboards would be a great way to fill it. EATX support is clearly an afterthought in most cases, where chassis are fully designed and then measured after the fact to see if any EATX boards will fit, rather than being designed around 13” wide boards from the start.

The reason we’ve complained about this repeatedly is because we’ve run into three separate instances where EVGA’s boards require a larger-than-ATX case, and we then have to hunt through our inventory for an enclosure that will actually support the correct size of EATX and check it with a ruler to find out if it will fit. The SR-X doesn’t really count, since it uses the unique and ridiculously large 13.6x15 inch HPTX form factor, but the X299 Dark and SR3 are both considered EATX and were both troublesome, especially the SR3. We eventually gave up and tossed it in the gigantic case Intel shipped us to house the oversized Dominus Extreme. Speaking of which, the Dominus Extreme is advertised as being “ 14”x14” EEB/ATX Form Factor.” 14”x14” is neither EEB nor ATX, ASUS. Please stop. The one thing everyone can agree on, even EVGA, is that ATX, EATX, and EEB have a height of 12 inches.

The name “EATX” implies a standard, but it’s not a standard, it’s a free-for-all. Things would be a lot easier for everyone if motherboard manufacturers stuck to the dimensions of SSI-EEB without trying to wedge custom form factors in between, or correctly referred to 12”x10.5” boards as SSI-CEB. Then case manufacturers would have no reason to write “EATX (up to 11 inches)” in every single spec sheet for normal-sized mid towers, and customers would know at a glance exactly what they were getting. We use open benches for testing, so we’d prefer it if manufacturers made the leap and committed to true SSI-EEB for anything larger than ATX, but at the end of the day it’s the consumer’s opinion that matters. Let us know your thoughts on EATX and if you’ve found it to be as much of a pain in the ass as we have.

Editorial: Patrick Lathan
Host, Editorial: Steve Burke
Video: Keegan Gallick

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ATX VS EATX Motherboard Comparison

A motherboard in a computer plays a vital role in the overall performance of the system. It is the backbone that connects all the essential components like CPU, GPU, RAM, hard drive, etc. together in one circuit board to successfully run the applications.

The layout and shape of a motherboard are called the form factor. It determines the case type, power supply, and where the essential components will fit. The most common type of form factor found in industrial and domestic PCs is ATX.

Advanced Technology eXtended or ATX is a motherboard that was introduced in 1995 by Intel to improve the standardization of motherboards.

ATX motherboards are available in different sizes and have slightly different functionality. They are Micro-ATX, Mini-ATX, WATX, EATX, mobile ATX, and pico-ATX. It is important to learn the difference between these variants because some features of one ATX form factor may not be suitable for another type.

In this article, we would like to discuss the differences between ATX and EATX i.e., Extended ATX form factor, and see which one you should buy. So, without further ado, let’s begin.

What is ATX?

atx motherbaord

Advanced Technology eXtended or ATX is the most common form factor of a computer motherboard. It was introduced by Intel in 1995 to replace the standard form factor motherboard i.e., AT or Advanced Technology.

ATX is considered one of the major changes in computer enclosure, power supply, and motherboard as it allowed interchangeability of parts and improved standardization. AT design, which is the predecessor of ATX, was once a de facto standard but lacked in many specifications.

This is where ATX proved better than AT in terms of interface, speed, expansion and overall performance. However, the arrangements of individual components on the ATX board blocked airflow and creates heat issues. To solve this problem, Intel introduced another form factor, BTX (Balanced Technology eXtended) in 2004.

In 2006, Intel discontinued the development of BTX due to the following reasons:

  • People already invested in Advanced Technology eXtended (ATX) form factor and do not want any change in their system.
  • BTX technology was expensive than ATX.
  • Many users did not care too much about the cooling factor.

Due to these reasons, manufacturers and developers focused more on bringing ATX variations to the market. Most variants were smaller in size and the number of ports was reduced. However, the overall layout remained the same.

A full-sized ATX motherboard is 12 inches x 9.6 inches, which is the standard form factor of the mainboard. The dimensions of a Micro-ATX board are 9.6 inches x 9.6 inches making it a good option for a budget-friendly gaming PC.

An EATX board, as the name suggests, is a bigger variant of the ATX form factor. It is 12 inches x 13 inches and offers all the ATX standard features. The advantages of having this motherboard are dual-socket support, better heat dissipation, additional slots, etc.

ATX Pros and Cons

Let us now see what advantages and drawbacks does an ATX form factor has:


  • ATX comes with many slots and ports that allow easy expansion.
  • More number of ports and slots allow easy upgrade, without hindrance.
  • ATX cases come in a variety of styles.
  • Most gaming PCs are loaded with an ATX motherboard.


  • ATX board is heavy and large.
  • The components arrangement in an ATX board disturbs airflow, thus less cooling.
  • It is expensive.

What is EATX?

EATX motherboard

Extended ATX is the largest of all ATX variants. This motherboard is designed to build a powerful PC system. Its configuration allows it to work alongside full tower cases and provide ample space and features.

The massive size of this motherboard not only allows expansion but also offers a good breathing room for essential components. This affects the overclocking of the system, thus improving the performance.

EATX motherboards are perfect for enthusiastic gamers or professional production workers (graphic designers, video editors, etc.) However, to enjoy such utilities you will have to pay an enormous amount.

EATX Pros and Cons

If your budget is high and you care more about the performance, here are some advantages that you will get from an EATX. Plus, pay attention to the drawbacks to alter your decision.


  • It has a massive amount of space to install the memory.
  • More expansion port means more GPUs, hence a better gaming experience.
  • The large size of the board cools the components and offers fantastic overclocking.


  • It requires a heavy budget.
  • EATX is not suitable for hobbyist gamers or editors unless you have a lot of money.
  • Their large size and features can be a bit overkill for many users.

Difference between ATX and EATX

Let us see the differences between an ATX and EATX form factor with the help of a table representation.

Features and SpecsATX MotherboardEATX Motherboard
Full-formAdvanced Technology eXtended Extended ATX
DefinitionATX is the standard form factor of the motherboard.EATX is nothing but a type of ATX with a bigger size.
Motherboard TypeAs of 2021, it is the de facto standard of the motherboard.EATX is the largest variant of the ATX board.
Cooling & OverclockingATX board arrangement can block the airway and affect cooling.EATX, due to its massive size offers fantastic cooling and overclocking.
Price ATX will cost less than EATX, but more than Micro-ATX.Expensive than ATX
Current StatusIt is common in domestic and industrial computers.It is mostly used by competitive gamers or professionals.


When we talk about ATX vs EATX, it is important to compare their sizes. An ATX motherboard which is the standard form factor has dimensions of 12 inches x 9.6 inches.

EATX, which is the largest variant of ATX is slightly bigger from the right side. It has dimensions of 12 inches x 13 inches. The larger size of this variant makes it a perfect option for server work.

As the size of the EATX board is larger, components installed in the board get good airflow, thus less heating. Plus, a system with an EATX mainboard is easier to use as the large size allows more space for GPU to fit in.

ATX VS EATX: Functionality

In terms of functionality, EATX performs better than ATX, how? Because EATX comes in a larger size, this means you get additional ports and slots for components.

In an ATX board, you will usually find 3-4 PCI-e x 16 ports and 4 RAM slots, whereas in an EATX board, you will find 4-8 PCI-e x 16 ports and 6-8 RAM slots.

Though EATX performs better than the ATX form factor, but is it suitable for all users? Well, let’s find out in the next section.

Which Should You Buy?

If you are confused about which motherboard should you go for, there is a rule of thumb to make your decision easy.

The type of motherboard you choose greatly depends on your needs. For example, if you are a hardcore competitive gamer, you will need a powerful PC system with dual graphics cards and better cooling, hence a larger motherboard (EATX). However, if you are a hobbyist gamer, a standard motherboard (ATX or smaller) should be fine for you.

The bottom line is, if you are willing to spend a large amount of money to upgrade from ATX to EATX, you can enjoy the following advantages:

  1. Better heat dissipation.
  2. Additional slots for more upgrades.
  3. Better gaming experience.
  4. Faster performance of various applications.

That being said, it will be wise to leave the EATX form factor for Professionals as this board can be overkill for many users.

Motherboard Form Factors


Motherboard and power supply configuration

This article is about the computer form factor. For other uses, see ATX (disambiguation).

Comparison of some common motherboardform factors (pen for scale)

ATX (Advanced Technology eXtended) 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.[1] Other standards for smaller boards (including microATX, FlexATX, nano-ITX, and mini-ITX) 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 (305 × 244 mm), 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.[2] The most recent ATX12V power supply unit specification is 2.53,[3] released in June 2020. EATX (Extended ATX) is a bigger version of the ATX motherboard with 12 × 13 in (305 × 330 mm) dimensions. While some dual CPU socket motherboards have been implemented in ATX, the extra size of EATX makes it the typical form factor for dual socket systems, and with sockets that support four or eight memory channels, for single socket systems with a large number of memory slots.

In 2004, Intel announced the BTX (Balanced Technology eXtended) standard, intended as a replacement for ATX. While some manufacturers adopted the new standard, Intel discontinued any future development of BTX in 2006. As of 2021[update], the ATX design still remains the de facto standard for personal computers.


ATX I/O plates for motherboard rear connectors

On the back of the computer case, some major changes were made to the AT standard. Originally AT style cases had only a keyboard connector and expansion slots for add-on card backplates. Any other onboard interfaces (such as serial and parallel ports) had to be connected via flying leads to connectors which were mounted either on spaces provided by the case or brackets placed in unused expansion slot positions.

ATX allowed each motherboard manufacturer to put these ports in a rectangular area on the back of the system with an arrangement they could define themselves, though a number of general patterns depending on what ports the motherboard offers have been followed by most manufacturers. Cases are usually fitted with a snap-out panel, also known as an I/O plate or I/O shield, in one of the common arrangements. If necessary, I/O plates can be replaced to suit a motherboard that is being fitted; the I/O plates are usually included with motherboards not designed for a particular computer. The computer will operate correctly without a plate fitted, although there will be open gaps in the case which may compromise the EMI/RFI screening and allow ingress of dirt and random foreign bodies. Panels were made that allowed fitting an AT motherboard in an ATX case. Some ATX motherboards come with an integrated I/O plate.

ATX also made the PS/2-stylemini-DIN keyboard and mouse connectors ubiquitous. AT systems used a 5-pin DIN connector for the keyboard and were generally used with serial port mice (although PS/2 mouse ports were also found on some systems). Many modern motherboards are phasing out the PS/2-style keyboard and mouse connectors in favor of the more modern Universal Serial Bus. Other legacy connectors that are slowly being phased out of modern ATX motherboards include 25-pin parallel ports and 9-pin RS-232serial ports. In their place are onboard peripheral ports such as Ethernet, FireWire, eSATA, audio ports (both analog and S/PDIF), video (analog D-sub, DVI, HDMI, or DisplayPort), extra USB ports, and Wi-Fi.

A notable issue with the ATX specification was that it was last revised when power supplies were normally placed at the top, rather than the bottom, of computer cases. This has led to some problematic standard locations for ports, in particular the 4/8 pin CPU power, which is normally located along the top edge of the board to make it convenient for top mounted power supplies. This makes it very difficult for cables from bottom mounted power supplies to reach, and commonly requires a special cutout in the back plane for the cable to come in from behind and bend around the board, making insertion and wire management very difficult. Many power supply cables barely reach or fail to reach, or are too stiff to make the bend, and extensions are commonly required due to this placement.


"EATX" redirects here. For the electronic automatic transaxle, see automatic transmission.

Main article: Computer form factor

ATX, Mini-ITX, and AT motherboard compatible dimensions and bore positions
ATX motherboard size comparison; rear is on left.

  FlexATX(229 × 191 mm)

  microATX(244 × 244 mm)

  Mini ATX(284 × 208 mm)

  Standard ATX(305 × 244 mm)

  Extended ATX (EATX) (305 × 330 mm)

  WTX(356 × 425 mm)

Several ATX-derived designs have been specified that use the same power supply, mountings and basic back panel arrangement, but set different standards for the size of the board and number of expansion slots. Standard ATX provides seven slots at 0.8 in (20 mm) spacing; the popular microATX size removes 2.4 inches (61 mm) and three slots, leaving four. Here width refers to the distance along the external connector edge, while depth is from front to rear. Note each larger size inherits all previous (smaller) colors area.

Note: AOpen has conflated the term Mini ATX with a more recent 15 × 15 cm (5.9 × 5.9 in) design. Since references to Mini ATX have been removed from ATX specifications since the adoption of microATX, the AOpen definition is the more contemporary term and the one listed above is apparently only of historical significance. This sounds contradictory to the now common Mini-ITX standard ( 17 × 17 cm (6.7 × 6.7 in) ), which is why referring to such a product as Mini ATX is only going to confuse people. A number of manufacturers have added one, two or three additional expansion slots (at the standard 0.8 inch spacing) to the standard 12-inch ATX motherboard width.

Form factors considered obsolete in 1999 included Baby-AT, full size AT, and the semi-proprietary LPX for low-profile cases. Proprietary motherboard designs such as those by Compaq, Packard-Bell, Hewlett Packard and others existed, and were not interchangeable with multi-manufacturer boards and cases. Portable and notebook computers and some 19-inch rackmount servers have custom motherboards unique to their particular products.[4]

Form factor Originated Date Max. size[a]
width × depth
Slots Notes
(typical usage, Market adoption, etc.)
ATX Intel 1995 12 × 9.6 in (305 × 244 mm) 7 [2]Original, successor to AT motherboard
Proprietary, specific to crypto-mining specific motherboards?? 2011 12 × 8 in (305 × 203 mm) 3 3 double-slot add-in cards with 1 slots of free space in between
SSI CEBSSI? 12 × 10.5 in (305 × 267 mm) 7 Compact Electronics Bay
SSI MEBSSI 2011 16.2 × 13 in (411 × 330 mm) 12 Midrange Electronics Bay
SSI EEBSSI ? 12 × 13 in (305 × 330 mm) 7 Enterprise Electronics Bay
SSI TEBSSI ? 12 × 10.5 in (305 × 267 mm) 7 Thin Electronics Bay, for rack-mount, has board component height specification
microATXIntel 1997 9.6 × 9.6 in (244 × 244 mm) 4 Fits in ATX, and EATX cases.
FlexATXIntel 1997 9 × 7.5 in (229 × 191 mm) 3
Extended ATX (standard) Supermicro / Asus? 12 × 13 in (305 × 330 mm) 7 Screw holes not completely compatible with some ATX cases. Designed for dual CPUs, and quad double slot video cards.
Extended ATX (commonly) Un­known ? 12 × 10.1 in (305 × 257 mm)
12 × 10.4 in (305 × 264 mm)
12 × 10.5 in (305 × 267 mm)
12 × 10.7 in (305 × 272 mm)
7 ATX pattern screw holes
EE-ATX Supermicro ? 13.68 × 13 in (347 × 330 mm) 7 Enhanced Extended ATX
Ultra ATXFoxconn 2008 14.4 × 9.6 in (366 × 244 mm) 10 Intended for multiple double-slot video cards, and dual CPUs.
XL-ATX EVGA2009 13.5 × 10.3 in (343 × 262 mm) 9
XL-ATX Gigabyte 2010 13.58 x 10.31 in (345 x 262 mm) 7
XL-ATX MSI2010 13.6 × 10.4 in (345 × 264 mm) 7
WTXIntel 1998 14 × 16.75 in (356 × 425 mm). 9 Discontinued 2008
Mini-ITXVIA2001 6.7 x 6.7in (170 × 170 mm). 1 Originally designed for home theatre or other fanless applications
Mini-DTXAMD2007 8 × 6.7 in (203 × 170 mm) 2 Derived from Mini-ITX and DTX
BTXIntel 2004 12.8 × 10.5 in (325 × 267 mm) 7 Canceled 2006. Also micro, nano, and pico variants. Not generally compatible with ATX mounting.
HPTX EVGA 2010 13.6 × 15 in (345 × 381 mm) 6 Dual processors, 12 RAM slots
SWTXSupermicro 2006 16.48 × 13 in (419 × 330 mm)
and others
5 Quad processors, not compatible with ATX mounting

Although true E-ATX is 12 × 13 in (305 × 330 mm) most motherboard manufacturers also refer to motherboards with measurements 12 × 10.1 in (305 × 257 mm), 12 × 10.4 in (305 × 264 mm), 12 × 10.5 in (305 × 267 mm) and 12 × 10.7 in (305 × 272 mm) as E-ATX. While E-ATX and SSI EEB (Server System Infrastructure (SSI) Forum's Enterprise Electronics Bay (EEB)) share the same dimensions, the screw holes of the two standards do not all align; rendering them incompatible.[citation needed]

In 2008, Foxconn unveiled a Foxconn F1 motherboard prototype, which has the same width as a standard ATX motherboard, but an extended 14.4" length to accommodate 10 slots.[5] The firm called the new 14.4 × 9.6 in (366 × 244 mm) design of this motherboard "Ultra ATX"[6] in its CES 2008 showing. Also unveiled during the January 2008 CES was the Lian Li Armorsuit PC-P80 case with 10 slots designed for the motherboard.[7]

The name "XL-ATX" has been used by at least three companies in different ways:

  • In September 2009, EVGA Corporation had already released a 13.5 × 10.3 in (343 × 262 mm) "XL-ATX" motherboard as its EVGA X58 Classified 4-Way SLI.[8]
  • Gigabyte Technology launched another XL-ATX motherboard, with model number GA-X58A-UD9 in 2010 measuring at 13.6 × 10.3 in (345 × 262 mm), and GA-X79-UD7 in 2011 measuring at 12.8 × 10.0 in (324 × 253 mm). In April 2010, Gigabyte announced its 12.8 × 9.6 in (325 × 244 mm) GA-890FXA-UD7 motherboard that allowed all seven slots to be moved downward by one slot position. The added length could have allowed placement of up to eight expansion slots, but the top slot position is vacant on this particular model.
  • MSI released MSI X58 Big Bang in 2010, MSI P67 Big Bang Marshal in 2011, MSI X79 Xpower Big Bang 2 in 2012 and MSI Z87 Xpower in 2013 all of them are 13.6 × 10.4 in (345 × 264 mm). Although these boards have room for additional expansion slots (9 and 8 total, respectively), all three provide only seven expansion connectors; the topmost positions are left vacant to provide more room for the CPU, chipset and associated cooling.

In 2010, EVGA Corporation released a new motherboard, the "Super Record 2", or SR-2, whose size surpasses that of the "EVGA X58 Classified 4-Way SLI". The new board is designed to accommodate two Dual QPI LGA1366 socket CPUs (e.g. Intel Xeon), similar to that of the Intel Skulltrail motherboard that could accommodate two Intel Core 2 Quad processors and has a total of seven PCI-E slots and 12 DDR3 RAM slots. The new design is dubbed "HPTX" and is 13.6 × 15 in (345 × 381 mm).[9]

Power supply[edit]

See also: Power supply unit (computer)

The ATX specification requires the power supply to produce three main outputs, +3.3 V, +5 V and +12 V. Low-power −12 V and +5 VSB (standby) supplies are also required. The −12 V supply is primarily used to provide the negative supply voltage for RS-232 ports and is also used by one pin on conventional PCI slots primarily to provide a reference voltage for some models of sound cards. The 5 VSB supply is used to produce trickle power to provide the soft-power feature of ATX when a PC is turned off, as well as powering the real-time clock to conserve the charge of the CMOS battery. A −5 V output was originally required because it was supplied on the ISA bus; it was removed in later versions of the ATX standard, as it became obsolete with the removal of the ISA bus expansion slots (the ISA bus itself is still found in any computer which is compatible with the old IBM PC specification (e.g., not found in the PlayStation 4.[10])

Originally, the motherboard was powered by one 20-pin connector. An ATX power supply provides a number of peripheral power connectors and (in modern systems) two connectors for the motherboard: an 8-pin (or 4+4-pin) auxiliary connector providing additional power to the CPU and a main 24-pin power supply connector, an extension of the original 20-pin version. 20-pin MOLEX 39-29-9202 at the motherboard. 20-pin MOLEX 39-01-2200 at the cable. The connector pin pitch is 4.2 mm (one sixth of an inch).

Pinouts of ATX 2.x motherboard power connectors, 24-pin (top) and four-pin "P4" (bottom), as viewed into mating side of the plugs[11]
24-pin ATX motherboard power plug; pins 11, 12, 23 and 24 form a detachable separate four-pin plug, making it backward-compatible with 20-pin ATX receptacles
Color Signal[A]Pin[B]Pin[B][C]Signal[A]Color
Orange +3.3 V 1 13 +3.3 V Orange
+3.3 V sense[D]Brown
Orange +3.3 V 2 14 −12 V Blue
Black Ground 3 15 Ground Black
Red +5 V 4 16 Power on[E]Green
Black Ground 5 17 Ground Black
Red +5 V 6 18 Ground Black
Black Ground 7 19 Ground Black
Grey Power good[F]8 20 Reserved[G]None
Purple +5 V standby 9 21 +5 V Red
Yellow +12 V 10 22 +5 V Red
Yellow +12 V 11 23 +5 V Red
Orange +3.3 V 12 24 Ground Black
  1. ^ ab  Light-blue background denotes control signals.
  2. ^ ab  Light-green background denotes the pins present only in the 24-pin connector.
  3. ^In the 20-pin connector, pins 13–22 are numbered 11–20 respectively.
  4. ^Supplies +3.3 V power and also has a second low-current wire for remote sensing.[12]
  5. ^A control signal that is pulled up to +5 V by the PSU and must be driven low to turn on the PSU.
  6. ^A control signal that is low when other outputs have not yet reached, or are about to leave, correct voltages.
  7. ^Formerly −5 V (  white wire), absent in modern power supplies; it was optional in ATX and ATX12V v1.2 and deleted since v1.3.
Green PS_ON#1 6 PWR_OKGray
Black COM 2 7 +12 VSB Purple
Black COM 3 8 +12 V1 DC Yellow
Black COM 4 9 +12 V1 DC Yellow
TBD Reserved 5 10 +12 V1 DC
Voltage Sensing Pin
on PS cable
Male/vertical header
on PCB
extender cable

Four wires have special functions:

  • PS_ON# (power on) is a signal from the motherboard to the power supply. When the line is connected to ground (by the motherboard), the power supply turns on. It is internally pulled up to +5 V inside the power supply.[2][13]
  • PWR_OK ("power good") is an output from the power supply that indicates that its output has stabilized and is ready for use. It remains low for a brief time (100–500 ms) after the PS_ON# signal is pulled low.[14]
  • +5 VSB (+5 V standby) supplies power even when the rest of the supply wire lines are off. This can be used to power the circuitry that controls the power-on signal.
  • +3.3 V sense should be connected to the +3.3 V on the motherboard or its power connector. This connection allows remote sensing of the voltage drop in the power-supply wiring. Some manufacturers also provided a +5 V sense wire (typically colored pink) connected to one of the red +5 V wires on some models of power supply; however, the inclusion of such wire was a non-standard practice and was never part of any official ATX standard.

Generally, supply voltages must be within ±5% of their nominal values at all times. The little-used negative supply voltages, however, have a ±10% tolerance. There is a specification for ripple in a 10 Hz–20 MHz bandwidth:[2]

Supply (V)ToleranceRange, min. to max. (V)Ripple, p. to p., max. (mV)
+5±5% (±0.25 V)+4.75 V to +5.25050
−5±10% (±0.50 V)−4.50 V to −5.50050
+12±5% (±0.60 V)+11.40 V to +12.60120
−12±10% (±1.20 V)−10.80 V to −13.20120
+3.3±5% (±0.165 V)+3.135 V to +3.465050
+5 standby±5% (±0.25 V)+4.75 V to +5.25050

The 20–24-pin Molex Mini-Fit Jr. has a power rating of 600 volts, 8 amperes maximum per pin (while using 18 AWG wire).[15] As large server motherboards and 3D graphics cards have required progressively more and more power to operate, it has been necessary to revise and extend the standard beyond the original 20-pin connector, to allow more current using multiple additional pins in parallel. The low circuit voltage is the restriction on power flow through each connector pin; at the maximum rated voltage, a single Mini-Fit Jr pin would be capable of 4800 watts.

Physical characteristics[edit]

ATX power supplies generally have the dimensions of 150 × 86 × 140 mm (5.9 × 3.4 × 5.5 in),[16]: 23–24  with the width and height being the same as the preceding LPX (Low Profile eXtension) form factor (which are often incorrectly referred to as "AT" power supplies due to their ubiquitous use in later AT and Baby AT systems, even though the actual AT and Baby AT power supply form factors were physically larger) and share a common mounting layout of four screws arranged on the back side of the unit. That last dimension, the 140 mm depth, is frequently varied, with depths of 160, 180, 200 and 230 mm used to accommodate higher power, larger fan and/or modular connectors.

Main changes from AT and LPX designs[edit]

Power switch[edit]

Original AT cases (flat case style) have an integrated power switch that protruded from the power supply and sits flush with a hole in the AT chassis. It utilizes a paddle-style DPST switch and is similar to the PC and PC-XT style power supplies.

Later AT (so-called "Baby AT") and LPX style computer cases have a power button that is directly connected to the system computer power supply (PSU). The general configuration is a double-pole latching mains voltage switch with the four pins connected to wires from a four-core cable. The wires are either soldered to the power button (making it difficult to replace the power supply if it failed) or blade receptacles were used.

Typical ATX 1.3 power supply. From left to right, the connectors are 20-pin motherboard, 4-pin "P4 connector", fan RPM monitor (note the lack of a power wire), SATA power connector (black), "Molex connector" and floppy connector.
Interior view in an ATX power supply

An ATX power supply is typically controlled by an electronic switch connected to the power button on the computer case and allows the computer to be turned off by the operating system. In addition, many ATX power supplies have an equivalent-function manual switch on the back that also ensures no power is being sent to the components. When the switch on the power supply is turned off, however, the computer cannot be turned on with the front power button.

Power connection to the motherboard[edit]

The power supply's connection to the motherboard was changed from the older AT and LPX standards; AT and LPX had two similar connectors that could be accidentally interchanged by forcing the different keyed connectors into place, usually causing short-circuits and irreversible damage to the motherboard (the rule of thumb for safe operation was to connect the side-by-side connectors with the black wires together). ATX uses one large, keyed connector which can not be connected incorrectly. The new connector also provides a 3.3 volt source, removing the need for motherboards to derive this voltage from the 5 V rail. Some motherboards, particularly those manufactured after the introduction of ATX but while LPX equipment was still in use, support both LPX and ATX PSUs.[17]

If using an ATX PSU for purposes other than powering an ATX motherboard, power can be fully turned on (it is always partly on to operate "wake-up" devices) by shorting the "power-on" pin on the ATX connector (pin 16, green wire) to a black wire (ground), which is what the power button on an ATX system does. A minimum load on one or more voltages may be required (varies by model and vendor); the standard does not specify operation without a minimum load and a conforming PSU may shut down, output incorrect voltages, or otherwise malfunction, but will not be hazardous or damaged.[18] An ATX power supply is not a replacement for a current-limited bench laboratory DC power supply, instead it is better described as a bulk DC power supply.[19]


The original ATX specification called for a power supply to be located near to the CPU with the power supply fan drawing in cooling air from outside the chassis and directing it onto the processor. It was thought that in this configuration, cooling of the processor would be achievable without the need of an active heatsink.[3] This recommendation was removed from later specifications; modern ATX power supplies usually exhaust air from the case.

ATX power supply revisions[edit]

Original ATX[edit]

ATX, introduced in late 1995, defined three types of power connectors:

  • 4-pin "Molex connector" — transferred directly from AT standard: +5 V and +12 V for P-ATA hard disks, CD-ROMs, 5.25 inch floppy drives and other peripherals.[20]
  • 4-pin Berg floppy connector — transferred directly from AT standard: +5 V and +12 V for 3.5 inch floppy drives and other peripherals.[21]
  • 20-pin Molex Mini-fit Jr. ATX motherboard connector — new to the ATX standard.
  • A supplemental 6-pin AUX connector providing additional 3.3 V and 5 V supplies to the motherboard, if needed. This was used to power the CPU in motherboards with CPU voltage regulator modules which required 3.3 volt and/or 5 volt rails and could not get enough power through the regular 20-pin header.

The power distribution specification defined that most of the PSU's power should be provided on 5 V and 3.3 V rails, because most of the electronic components (CPU, RAM, chipset, PCI, AGP and ISA cards) used 5 V or 3.3 V for power supply. The 12 V rail was only used by computer fans and motors of peripheral devices (HDD, FDD, CD-ROM, etc.)

ATX12V 1.x[edit]

While designing the Pentium 4 platform in 1999/2000, the standard 20-pin ATX power connector was found insufficient to meet increasing power-line requirements; the standard was significantly revised into ATX12V 1.0 (ATX12V 1.x is sometimes inaccurately called ATX-P4). ATX12V 1.x was also adopted by AMD Athlon XP and Athlon 64 systems. However, some early model Athlon XP and MP boards (including some server boards) and later model lower-end motherboards do not have the 4-pin connector as described below.

Numbering of the ATX revisions may be a little confusing: ATX refers to the design, and goes up to version 2.2 in 2004 (with the 24 pins of ATX12V 2.0) while ATX12V describes only the PSU. For instance, ATX 2.03 is pretty commonly seen on PSU from 2000 & 2001 and often include the P4 12V connector, even if the norm itself does not define it yet![2]

ATX12V 1.0

The main changes and additions in ATX12V 1.0 (released in February 2000) were:

  • Increased the power on the 12 V rail (power on 5 V and 3.3 V rails remained mostly the same).
  • An extra 4-pin mini fit JR (Molex 39-01-2040), 12-volt connector to power the CPU.[16]

Formally called the +12 V Power Connector, this is commonly referred to as the P4 connector because this was first needed to support the Pentium 4 processor.

Before the Pentium 4, processors were generally powered from the 5 V rail. Later processors operate at much lower voltages, typically around 1 V and some draw over 100 A. It is infeasible to provide power at such low voltages and high currents from a standard system power supply, so the Pentium 4 established the practice of generating it with a DC-to-DC converter on the motherboard next to the processor, powered by the 4-pin 12 V connector.

ATX12V 1.1

This is a minor revision from August 2000. The power on the 3.3 V rail was slightly increased and other smaller changes were made.

ATX12V 1.2

A relatively minor revision from January 2002. The only significant change was that the −5 V rail was no longer required (it became optional). This voltage was required by the ISA bus, which is no longer present on almost all modern computers.

ATX12V 1.3

Introduced in April 2003 (a month after 2.0). This standard introduced some changes, mostly minor. Some of them are:

  • Slightly increased the power on 12 V rail.
  • Defined minimal required PSU efficiencies for light and normal load.
  • Defined acoustic levels.
  • Introduction of Serial ATA power connector (but defined as optional).
  • Guidance for the −5 V rail was removed (but it was not prohibited).[22]

ATX12V 2.x[edit]

ATX12V 2.x brought a significant design change regarding power distribution. By analyzing the power demands of then-current PCs, it was determined that it would be much cheaper and more practical to power most PC components from 12 V rails, instead of from 3.3 V and 5 V rails.

In particular, PCI Express expansion cards take much of their power from the 12 V rail (up to 5.5 A), while the older AGP graphics cards took only up to 1 A on 12 V and up to 6 A on 3.3 V. The CPU is also driven by a 12 V rail, while it was done by a 5 V rail on older PCs (before the Pentium 4).

ATX12V 2.0

The power demands of PCI Express were incorporated in ATX12V 2.0 (introduced in February 2003), which defined quite different power distribution from ATX12V 1.x:

  • Most power is now provided on 12 V rails. The standard specifies that two independent 12 V rails (12 V2 for the four-pin connector and 12 V1 for everything else) with independent overcurrent protection are needed to meet the power requirements safely (some very high power PSUs have more than two rails; recommendations for such large PSUs are not given by the standard).
  • The power on 3.3 V and 5 V rails was significantly reduced.
  • The ATX motherboard connector was extended to 24 pins. The extra four pins provide one additional 3.3 V, 5 V and 12 V circuit.
  • The six-pin AUX connector from ATX12V 1.x was removed because the extra 3.3 V and 5 V circuits which it provided are now incorporated in the 24-pin ATX motherboard connector.
  • The power supply is required to include a Serial ATA power cable.
  • Many other specification changes and additions
ATX12V v2.01

This is a minor revision from June 2004. An errant reference for the −5 V rail was removed. Other minor changes were introduced.[23]

ATX12V v2.1

This is a minor revision from March 2005. The power was slightly increased on all rails. Efficiency requirements changed.

ATX12V v2.2

Also released in March 2005[2] it includes corrections and specifies High Current Series wire terminals for 24-pin ATX motherboard and 4-pin +12 V power connectors.

ATX12V v2.3

Effective March 2007. Recommended efficiency was increased to 80% (with at least 70% required) and the 12 V minimum load requirement was lowered. Higher efficiency generally results in less power consumption (and less waste heat) and the 80% recommendation brings supplies in line with new Energy Star 4.0 mandates.[24] The reduced load requirement allows compatibility with processors that draw very little power during startup.[25] The absolute over-current limit of 240 VA per rail was removed, allowing 12 V lines to provide more than 20 A per rail.[citation needed]

ATX12V v2.31

This revision became effective in February 2008. It added a maximum allowed ripple/noise specification of 400 millivolts to the PWR_ON and PWR_OK signals, requires that the DC power must hold for more than 1 millisecond after the PWR_OK signal drops, clarified country-specific input line harmonic content and electromagnetic compatibility requirements, added a section about Climate Savers, updated recommended power supply configuration charts, and updated the cross-regulation graphs.

ATX12V v2.32

This the unofficial name given to the later revisions of the v2.31 spec.[26]

ATX12V v2.4

The ATX12V 2.4 specifications were published in April 2013. It is specified in Revision 1.31 of the 'Design Guide for Desktop Platform Form Factors', which names this as ATX12V version 2.4.[27]

ATX12V v2.51

The specifications for ATXV12 2.51 were released in September 2017 and introduced support for Alternative Sleep Mode (ASM) which supersedes the traditional S3 power state. Windows 10 implements this functionality as Modern Standby.[3]

ATX12V v2.52

The specifications for ATXV12 2.52 were released in June 2018 introduces minor changes to the standard, most notably it requires power supply manufacturers to ensure power supplies with Alternative Sleep Mode (ASM) support are able to withstand power cycles every 180 seconds (480 times per day or 175,200 per year). Power supply fans are also recommended to turn on with at least a two second delay for an improved user experience.[28]

ATX12V v2.53

The specifications for ATXV12 2.53 were released in June 2020 and constitute another minor update to the ATX standard. ATXV12 2.53 makes further recommendations on efficiency and references the Energy StarComputers Specification Version 8.0 which was finalized in April 2020.[3][29]

ATX power supply derivatives[edit]


Standing for ATX 12-volt-only, this is a new specification published by Intel in 2019, aimed at pre-built systems in the first run, and possibly affecting DIY and "high expandability" systems (defined as a pre-built computer with a discrete GPU) when a market emerges. It was motivated by stricter power efficiency requirements by the California Energy Commission going into effect in 2021.[30] Several OEMs were already using a similar design with proprietary connectors and this effectively standardizes those.[31]

Under this standard, power supplies provide only a 12V output. ATX12VO introduces a new 10-pin connector to supply the motherboard, replacing the 24-pin ATX12V connector. This greatly simplifies power supplies, but moves DC-to-DC conversion and some connectors to the motherboard instead. Notably, SATA power connectors, which include 3.3V and 5V pins, need to move to the motherboard instead of being connected directly to the power supply.[31]


SFX is merely a design for a small form factor (SFF) power supply casing (such as those using microATX, FlexATX, nano-ITX, mini-ITX, and NLX), 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.[32]

Some manufacturers and retailers incorrectly market SFX power supplies as μATX or MicroATX power supplies. [33]

Some manufacturers make SFX-L dimensions of 125 × 63.5 × 130 mm to accommodate a 120 mm fan. [34]


Thin Form Factor is another small power supply design with standard ATX specification connectors. Generally dimensioned (W × H × D): 85 × 64 × 175 mm (3.34 × 2.52 × 6.89 in).[35][36]


Provides a WTX style motherboard connector which is incompatible with the standard ATX motherboard connector.

AMD GES[edit]

This is an ATX12V power supply derivative made by AMD to power its Athlon MP (dual processor) platform. It was used only on high-end Athlon MP motherboards. It has a special 8-pin supplemental connector for motherboard, so an AMD GES PSU is required for such motherboards (those motherboards will not work with ATX(12 V) PSUs).

a. ATX12V-GES 24-pin P1 motherboard connector. The pinout on the motherboard connector is as follows when viewing the motherboard from above:

PinSignalColour PinSignalColour
1212 VYellow 2412 VYellow
1112 VYellow 23GNDBlack
10GNDBlack 22GNDBlack
9GNDBlack 213.3 VOrange
83.3 VOrange 203.3 VOrange
73.3 VOrange 193.3 VOrange
6GNDBlack 18GNDBlack
5PS_ON_NGreen 17−12 VBlue
4GNDBlack 165 V SBPurple
3GNDBlack 15GNDBlack
25 VRed 145 VRed
15 VRed 135 VRed

b. ATX12V-GES 8-pin P2 motherboard connector. This pinout on the motherboard connector is as follows when viewing the motherboard from above:

PinSignalColour PinSignalColour
4GNDBlack 812 VYellow striped black
3GNDBlack 712 VYellow striped black
2PWR_OKGray 612 VYellow striped black
15 VRed 5GNDBlack


EPS12V is defined in Server System Infrastructure (SSI) and used primarily by SMP/multi-core systems such as Core 2, Core i7, Opteron and Xeon. It has a 24-pin ATX motherboard connector (same as ATX12V v2.x), an 8-pin secondary connector and an optional 4-pin tertiary connector. Rather than include the extra cable, many power supply makers implement the 8-pin connector as two combinable 4-pin connectors to ensure backwards compatibility with ATX12V motherboards.

Recent specification changes and additions[edit]

High-performance video card power demands dramatically increased during the 2000s and some high-end graphics cards have power demands that exceed AGP or PCIe slot capabilities. For these cards, supplementary power was delivered through a standard 4-pin peripheral or floppy power connector. Midrange and high-end PCIe graphics cards manufactured after 2004 typically use a standard 6 or 8-pin PCIe power connector directly from the PSU.

Interchanging PSUs[edit]

Although the ATX power supply specifications are mostly vertically compatible in both ways (both electrically and physically), there are potential issues with mixing old motherboards/systems with new PSUs and vice versa. The main issues to consider are the following:

  • The power allocation between 3.3 V, 5 V and 12 V rails is very different between older and newer ATX PSU designs, as well as between older and newer PC system designs.
  • Older PSUs may not have connectors which are required for newer PC systems to properly operate.
  • Newer systems generally have higher power requirements than older systems.

This is a practical guidance what to mix and what not to mix:

  • Older systems (before Pentium 4 and Athlon XP platforms) were designed to draw most power from 5 V and 3.3 V rails.
  • Because of the DC-DC converters on the motherboard that convert 12 V to the low voltages required by the Intel Pentium 4 and AMD Athlon XP (and subsequent) processors, such systems draw most of their power from the 12 V rail.
  • Original ATX PSUs have power distribution designed for pre-P4/XP PCs. They lack the supplemental 4-pin 12-volt CPU power connector, so they most likely cannot be used with P4/XP or newer motherboards. Adapters do exist but power drain on the 12 V rail must be checked very carefully. There is a chance it can work without connecting the 4-pin 12 V connector, but caution is advised.[37]
  • ATX12V 1.x PSUs have power distribution designed for P4/XP PCs, but they are also greatly suitable for older PCs, since they give plenty of power (relative to old PCs' needs) both on 12 V and on 5 V/3.3 V. It is not recommended to use ATX12V 1.x PSUs on ATX12V 2.x motherboards because those systems require much more power on 12 V than ATX12V 1.x PSUs provide.
  • ATX12V 2.x PSUs have power distribution designed for late P4/XP PCs and for Athlon 64 and Core Duo PCs. They can be used with earlier P4/XP PCs, but the power distribution will be significantly suboptimal, so a more powerful ATX12V 2.0 PSU should be used to compensate for that discrepancy. ATX12V 2.x PSUs can also be used with pre-P4/XP systems, but the power distribution will be greatly suboptimal (12 V rails will be mostly unused, while the 3.3 V/5 V rails will be overloaded), so this is not recommended.
  • Systems that use an ISA bus should have a PSU that provides the −5 V rail, which became optional in ATX12V 1.2 and was subsequently phased out by manufacturers.

Some proprietary brand-name systems require a matching proprietary power supply, but some of them may also support standard and interchangeable power supplies.


See also: Green computing and 80 Plus

Efficiency in power supplies means the extent to which power is not wasted in converting electricity from a household supply to regulated DC. Computer power supplies vary from around 70% to over 90% efficiency.

Various initiatives exist to improve the efficiency of computer power supplies. Climate Savers Computing Initiative promotes energy saving and reduction of greenhouse gas emissions by encouraging development and use of more efficient power supplies. 80 PLUS certifies a variety of efficiency levels for power supplies and encourages their use via financial incentives. Efficient power supplies also save money by wasting less power; as a result they use less electricity to power the same computer, and they emit less waste heat which results in significant energy savings on central air conditioning in the summer. The gains of using an efficient power supply are more substantial in computers that use a lot of power.

Although a power supply with a larger than needed power rating will have an extra margin of safety against overloading, such a unit is often less efficient and wastes more electricity at lower loads than a more appropriately sized unit. For example, a 900-watt power supply with the 80 Plus Silver efficiency rating (which means that such a power supply is designed to be at least 85-percent efficient for loads above 180 W) may only be 73% efficient when the load is lower than 100 W, which is a typical idle power for a desktop computer. Thus, for a 100 W load, losses for this supply would be 27 W; if the same power supply was put under a 450 W load, for which the supply's efficiency peaks at 89%, the loss would be only 56 W despite supplying 4.5 times the useful power.[38][39] For a comparison, a 500-watt power supply carrying the 80 Plus Bronze efficiency rating (which means that such a power supply is designed to be at least 82-percent efficient for loads above 100 W) may provide an 84-percent efficiency for a 100 W load, wasting only 19 W.[40]

See also[edit]


  1. ^For boards which take expansion slots, the length of the expansion card aligns with the depth of the system board. The case may support cards longer than the depth of the mainboard.


  1. ^Mark, Soper; Prowse, David; Mueller, Scott (September 2012). Authorized Cert Guide: CompTIA A+. Pearson Education. ISBN .
  2. ^ abcde"ATX Specification - Version 2.2"(PDF). Archived from the original(PDF) on 2012-07-25. Retrieved April 4, 2014.
  3. ^ abc"Power Supply Design Guide for Desktop Platform Form Factors, Revision 003". Intel. June 2020. Retrieved February 22, 2021.
  4. ^Scott Mueller, Upgrading and Repairing PCs, Eleventh Edition, Que Books, 1999, ISBN 0-7897-1903-7, page 1255
  5. ^"Foxconn F1 Motherboard Prototype". Archived from the original on 24 October 2014. Retrieved 18 November 2014.
  6. ^Thomas Soderstrom. "Foxconn Reveals X48, Ultra ATX, and Shamino". Tom's Hardware. Retrieved 18 November 2014.
  7. ^"Lian Li Armorsuit PC-P80R Spider Edition". TechPowerUp. Retrieved 18 November 2014.
  8. ^"The New 4-Way SLI Platform Has Arrived!". Retrieved 18 November 2014.
  9. ^"EVGA Corporation Super Record 2". Retrieved 18 November 2014.
  10. ^"Console Hacking 2016 – PS4: PC Master Race". 2016-12-27.
  11. ^"Power Supply Design Guide for Desktop Platform Form Factors, Revision 1.31"(PDF). Intel. April 2013. p. 26. Archived from the original(PDF) on October 21, 2014. Retrieved February 6, 2015.
  12. ^"ATX Specification Version 2.1"(PDF). Archived from the original(PDF) on 2003-09-24.
  13. ^"How to Convert a Computer ATX Power Supply to a Lab Power Supply (with video) - wikiHow". Retrieved 2013-08-17.
  14. ^"PCGuide - Ref - Power Supply - Functions". Archived from the original on 2013-08-28. Retrieved
  15. ^"Mini-Fit Jr. Power Connectors - Molex". Retrieved 18 November 2014.
  16. ^ ab"AT / ATX12V Power Supply Design Guide Version 1.1"(pdf). Intel Corporation. August 2000. p. 28. Archived(PDF) from the original on 2010-12-07. Retrieved 2011-03-11.
  17. ^"Example of a motherboard that can support connecting AT and ATX PSUs". Archived from the original on 13 December 2013. Retrieved 18 November 2014.
  18. ^"PC Power Supply Requirements and Troubleshooting Problems". RepRap project. September 19, 2018. Archived from the original on September 19, 2018.
  19. ^Using a Computer PSU; J. B. Calvert; University of Denver.
  20. ^"PC peripheral power connector pinout and signals @". Retrieved 18 November 2014.
  21. ^"PC floppy power connector pinout and signals @". Retrieved 18 November 2014.
  22. ^"ATX12V Power Supply Design Guide Version 1.3"(pdf). Intel Corporation. April 2003. p. 38. Retrieved 2013-03-24.
  23. ^"ATX12V Power Supply Design Guide Version 2.01"(PDF). Intel Corporation. June 2004. p. 44. Archived from the original(pdf) on 2009-11-22. Retrieved 2013-03-24.
  24. ^"Design Guide for Desktop Platform Form Factors, Intel Corp"(PDF). Archived from the original(PDF) on 2015-01-14. Retrieved 18 November 2014.
  25. ^"#138 - Question/Answer: ATX 12V 2.2 vs. ATX 12V 2.3". YouTube. Retrieved 18 November 2014.
  26. ^"Antec High Current Gamer Modular 750 W Review".
  27. ^"Power Supply Design Guide for Desktop Platform Form Factors"(PDF). Intel. April 2013. Archived(PDF) from the original on April 1, 2018. Retrieved April 1, 2018.
  28. ^"Power Supply Design Guide for Desktop Platform Form Factors Revision 002"(PDF). Intel. June 2018. Archived(PDF) from the original on March 13, 2020. Retrieved September 15, 2020.
  29. ^"Computers Specification Version 8.0". Energy Star. April 2020. Retrieved February 22, 2021.
  30. ^"How Intel is changing the future of power supplies with its ATX12VO spec". PCWorld. 2020-03-09. Retrieved 2020-04-13.
  31. ^ abLathan, Patrick (2020-04-10). "Intel ATX12VO vs. 12V Spec Explained & What Manufacturers Think". GamersNexus. Retrieved 2020-04-13.
  32. ^"SFX Form Factor". Archived from the original on 11 February 2001. Retrieved 18 November 2014.
  33. ^List of computer PSU form factors - SilverStone Technology Co., Ltd.
  34. ^SFX-L Computex 2017 roundup - Small Form Factor Network
  35. ^Modern Form Factors: EPS, TFX, CFX, LFX, And Flex ATX - Power Supply 101: A Reference Of Specifications
  36. ^Power Supplies TekSpek Guide - SCAN UK
  37. ^[1]Archived October 3, 2009, at the Wayback Machine
  38. ^Christoph Katzer (2008-09-22). "Debunking Power Supply Myths". AnandTech. p. 3. Retrieved 2014-10-07.
  39. ^"Cooler Master UCP Product Sheet"(PDF). Cooler Master. 2008. Retrieved 2014-10-11.
  40. ^Martin Kaffei (2011-10-10). "SilverStone Strider Plus – 500 W Modular Power". AnandTech. p. 4. Retrieved 2014-10-11.

External links[edit]

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