Should I choose Micro ATX (mATX) or ATX for my next Gaming PC?

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There are 2 popular form factors for gaming PC’s; Micro ATX and ATX. I’ve been asked many times before which form factor I recommend. By making this choice, we are determining the correct size motherboard for our requirements which in turn determines the size of the case. In this article, we look at the pros and cons of each to help you decide upon your next motherboard and case.

What is Micro ATX (mATX)?

mATX motherboards are a small form factor (SFF) that allows for installation within a compact case. While not the smallest form factor, mATX provides the necessary connectivity on the motherboard to cater to the needs of gamers. It tends to be a popular choice for those who are either making the most of a small space on their desk or prefer the look of the compact design. mATX motherboards do fit within ATX cases but it tends to look a little strange as it won’t take up the full space intended for an ATX board.

mATX boards will provide fewer expansion slots such as PCI-E (PCI Express) which are used for graphics cards, sound cards, storage expansion, wifi and TV/capture cards. Many of these uses duplicate the connections already available on the motherboard natively and would only really be used if you run out of connections or have a specialist need (i.e. game capture cards). As long as you know upfront what you are intending to connect or use the gaming PC for in addition to gaming, then an mATX setup will be suitable for nearly everyone.

I mentioned PCI-E but just wanted to clarify that every mATX board will have a PCI-E 16x slot for your graphics card.

An mATX build

What is ATX?

An ATX motherboard is a standard sized motherboard which fits in to an ATX case. People choose ATX primarily for the additional options it provides around motherboard and case selection but also for the connections on the board. Because the motherboard is larger, you’ll find additional slots for expansion cards or additional m.2 hard drive slots, for example. In addition, ATX is the choice for anyone who wants to run 2 graphics cards at once (known as SLI or crossfire). This is quite a niche use case and unlikely to be a requirement for the majority but nonetheless, ATX provides that option.

As ATX tends to be the standard size, you’ll have more choice when selecting your motherboard.

An ATX build

mATX vs ATX compared

When we comapre the form factors together, we find that the main difference is that the ATX board is 25% longer than the mATX version with both having the same overall width. These sizes are standard across all manufacturers.

ATXmATX
Dimensions12 × 9.6 in (305 × 244 mm)9.6 × 9.6 in (244 × 244 mm)
PCI-E Slots53
M.2 SSD Slots22

When comparing the motherboards available for a Ryzen build using the X570 and B550 chipsets, I found there was much more choice when opting for the larger, ATX, size.

ManufacturerATXmATX
Asus152
ASRock226
Gigabyte124
MSI169
Total6521

Below are comparisons side by side of the Corsair 280x RGB and Corsair iCUE 465X RGB. As you can see by the pictures, the mATX case is shorter than the ATX case but wider as the PSU is positioned behind the motherboard rather than below it.

Performance

It’s unlikely you’ll see increased performance between different sized motherboards because they use the same chipset. However, for those who want to overlock, ATX motherboards tend to be a better choice due to having more space for additional heatsinks and more space within the case for hot air to be removed from the components.

Size considerations

An mATX case will provide less space to work in and less overall space for your components. A large graphics card may not fit in a mATX case as could be too long, although many manufacturers create smaller versions of their graphics card to cater for the smaller case.

You should always check how much space you have available for your cooler, especially with a mATX case. Some of the higher-end air coolers are very tall and would not allow for the window to be attached. Infact, some are so big that I’ve had this problem with an ATX case too. In this situation, it may be better to instead choose a low profile cooler as many perform just as well as the larger ones.

For those using planning to use an all in one water cooling solution (AIO), you should check to make sure the radiator will fit in the case. In my previous build using the Corsair 280x RGB and Corsair H100i RGB Platinum, I was limited to where I could mount the radiator. Luckily this didn’t present a problem for me!

Other components such as the power supply and memory should fit just fine between both size cases although there are low profile options available for both.

Cable management and airflow

As mATX cases are smaller, you have less room to build in. The aim of the mATX is to allow you to build a high performing gaming pc within a smaller footprint. You will therefore find that cable management might be trickier and it you may need to think ahead to make sure cables are correctly routed through the case rather than having to start again.

Each case has their own characteristics when it comes to airflow but in my experience I found that the mATX case ran slightly hotter than an ATX case due to the smaller internal area.

The first screenshot shows my graphics card running in excess of 80 degrees within the Corsair 280x RGB.

In comparison, I found the graphics card temperature dropped slightly when using the Corsair iCue 465x RGB case.

Cost

I compared the equivalent motherboards across both form factors and found the ATX form factor to be marginally more expensive. I’m not sure the differences are significant enough to have a material impact on somebody’s decision but it may allow for some of the budget to be spent elsewhere.

MotherboardB550M (mATX)B550 (ATX)
MSI MAG Range£152.69 (Amazon)£164.99 (Amazon)
ASUS TUF Gaming Range£162.33 (Amazon)£174.99 (Amazon)
Gigabyte Aorus Pro Range£174.04 (Amazon)£199.99 (Amazon)
ASRock Steel Legend Range£129.73 (Amazon)£181.24 (Amazon)

Conclusion

My conclusion is that your choice will most likely be determined by factors such as the space on your desk and the preference to try a smaller mATX case. Other factors include needing a case with higher air flow to keep temperatures low, whether you want to overclock and whether you are confident trying to neatly arrange your cables in a smaller space.