EATX, ATX, Micro ATX, and Mini ITX: What’s the Difference?

When purchasing a computer, either as a pre-built unit or as individual pieces, you’ll come across a somewhat confusing specification. It’ll claim that the PC is “ATX” or “Micro ATX”, without really explaining what this means. Unfortunately, these confusing initialisms are very important to understand when purchasing a computer! While getting the wrong kind of PC won’t spell disaster for you, it could potentially hamper any future plans you have with the PC. So what do these strange terms mean?

What This Specification Means


These initialisms are referring to what’s called the “form factor” of the motherboard. Motherboards can come in all shapes and sizes to fit in an array of devices, from supercomputers to mobile phones. As such, there’s a need to differentiate all the different ways motherboards are made.

As you might expect, there are quite a lot of form factors out there, each one designed to fit a specific role. For the sake of this article, however, we’ll only be focusing on the ones you’re most likely to encounter when purchasing a PC or a motherboard: EATX, ATX, Micro ATX, and Mini ITX.

What Does Each One Mean?

To start, let’s begin with the “standard”-sized motherboard which is the ATX. ATX stands for “Advanced Technology eXtended” and was developed as far back as 1995. If you own, or have owned, a regular-sized PC, there’s a good chance it has an ATX motherboard. This makes ATX the “regular” choice when purchasing a PC or motherboard.

From ATX, motherboards get either bigger or smaller in size. Going upward, you have the EATX motherboard (Extended ATX) which adds more to the ATX board and is slightly larger as a result. Going the other way, you have the Micro ATX which is smaller than the ATX. After that is the Mini ITX (“Information Technology eXtended”) which is even smaller than the Micro ATX. This might be confusing, as the “Micro” board is larger than the “Mini” one, so be careful with this!

How Are They Different?

So now we know that the obvious difference between these four motherboards is their size: EATX is the biggest, followed by ATX, then Micro ATX, and finally Mini ITX. But why do we have differently-sized motherboards in the first place? What advantages and disadvantages come with different sizes?

Case Size


For one, having a smaller motherboard allows you to have a smaller computer on the whole. If you take a look inside a PC’s case, you’ll see that a lot of its height is taken up by the motherboard alone. If you want a smaller computer, it’s a good idea to start with a smaller motherboard!

Micro ATX and Mini ITX are choice picks for people who want smaller computers. Small PCs are great if you want something that’s portable or as a server or media center that doesn’t take up much room. Just remember that components designed for ATX computers might not fit inside a smaller case.

On a regular occasion, a case designed for a specific form factor can also support smaller ones. For example, ATX cases are often designed so they can also hold Micro ATX and/or Mini ITX motherboards. Make sure you check the manufacturer’s specifications before buying a PC case that’s a different size than your motherboard.


The smaller size does come at a cost, however. Smaller motherboards are made possible by removing extension slots on the motherboard itself. The result is a motherboard which fits in smaller cases but doesn’t have the upgradability freedom that the larger form factors have.

The change from ATX to Micro ATX loses some of the PCI slots. ATX motherboards come with around six PCI slots (usually 3x PCI-E x16 and 3x PCI-E x1, but this can vary between models), while Micro ATX comes with around three (1x PCI-E x16 and 2x PCI-E x1). This means less space for additions such as graphics, sound, capture, and network cards. Mini ITX boards usually only have the one PCI-E x16 slot.

Sometimes there will be a decrease in RAM slots as well. ATX to Micro ATX can go from four slots down to two, although this doesn’t always happen. Mini ITX often comes with only two RAM slots, although some have managed four. USB ports can also take a hit as a result of the smaller board.

Of course, the opposite is true: The larger EATX boards will come with more functionality. At the very least, they’ll usually sport four or more PCI-E x16 slots which makes them a great choice if you have big plans for your PCI-E ports. In short, if you’re looking for a PC with lots of ports and upgradability options, stick with ATX or EATX over the smaller choices.



While not always the case, Micro ATX computers and motherboards tend to be the cheapest option. If you’re looking for a PC you have no interest in upgrading or installing extra hardware into, you might be able to save yourself some money by going for a smaller motherboard. Just make sure you don’t want to add extra components in the future, otherwise you might find yourself purchasing ATX later down the line to fit your needs.

Are Smaller Boards “Slower”?

Despite their size, you shouldn’t find that smaller motherboards “run slower” than larger ones. Of course, going smaller does mean you might sacrifice PCI-E and RAM slots which will mean the computer’s potential power is less than its larger brethren. You may also find smaller boards don’t handle overclocking and high-end usage as well as ATX and EATX boards can. In terms of smaller boards being slower “by nature,” however, they shouldn’t be.

Welcome a Board

The form factor of a PC can be a confusing topic. Now you know their main differences, how they’re used, and which one will suit you the most.

Is a motherboard’s form factor a crucial purchase point? Or does it not make much of a difference for you? Let us know below!

Simon Batt Simon Batt

Simon Batt is a Computer Science graduate with a passion for cybersecurity.