ATX vs SFX PSU : How do they differ?


When it comes to building a gaming PC, size matters. If you need a powerful set-up in a small form factor chassis, then an SFX power supply unit (PSU) is the ideal solution. SFX PSUs are incredibly powerful for their small size and offer great flexibility with modular cables that reduce cable clutter.

In this article, we’ll compare the features and benefits of ATX vs. SFX PSUs so you can decide which one is best for your gaming needs.

Let’s dive in!

What are ATX PSUs?

You need to power your dream gaming PC but don’t want to take up too much space? An ATX PSU might be the answer – it’s a standard-sized box that can provide up to 300W of power and fits in most cases.

The ATX standard measures 150 x 86 x 140 mm, and features a 24-pin main connector that plugs into the motherboard, as well as various peripheral connectors that power the CPU, GPU, storage devices, fans and other components.

But if you’re after more than just power efficiency – like saving on additional space – an SFX PSU may be the better option for you.

SFX PSUs are typically smaller than their ATX counterparts – measuring at 100mm x 125mm x 63.5mm – yet still offer up to 800W of power so they are perfect for high-powered small gaming set-ups.

Plus, since they’re designed for minimal space usage, these PSUs tend to come with fully modular cables so you can pick and choose what cables you use and reduce cable clutter in your system build.

So if you’re looking to save on extra space while making sure your rig is running optimally with plenty of juice coming through it – investing in an SFX PSU could be the way forward for your dream gaming PC!

What are SFX PSUs?

If you’re looking to save on space while providing plenty of power, an SFX PSU is the perfect solution – its small size allows it to fit into even the tightest of cases, while still delivering up to 800W.

What’s more, SFX PSUs typically come fully modular, meaning you can pick and choose which cables to use for your build. This helps reduce unsightly cable clutter and makes building your PC easier and neater.

The SFX PSU standard is designed specifically for smaller PCs with limited space and cooling. Unlike ATX or EPS PSUs that have larger sizes and require more cables and connectors, an SFX PSU fits neatly into any mini-ITX or micro-ATX case without taking up too much room.

It also has a 24-pin main connector that plugs directly into the motherboard, as well as fewer peripheral connectors than ATX or EPS PSUs.

SFX PSUs are capable of providing up to 250 W of power but some models can go higher depending on their efficiency and quality. So if you’re looking for a smaller form factor power supply unit with plenty of wattage for your dream gaming PC – look no further than an SFX PSU!

ATX vs SFX: Size

When it comes to saving space in your PC build, an SFX PSU is the perfect solution, packing plenty of punch into a tiny package that’ll fit seamlessly into any mini-ITX or micro-ATX case. SFX power supplies are physically smaller than ATX power supplies and measure at 100mm x 125mm x 63.5mm, but still offer up to 800W of power. That means they’re perfect for high-powered small gaming set-ups where space could be limited. They’re also designed to reduce cable clutter since they’re fully modular; you can pick and choose what cables you use resulting in less unsightly wires throughout your system.

Not only do SFX PSUs save on space but they also have other benefits too; their smaller size allows them to run cooler than larger ATX PSUs meaning that there’s less need for bulky fans that can be noisy and distracting when gaming or working on complex tasks like video editing or streaming. Furthermore, as the components inside are compacted together there are fewer air pockets which means greater efficiency and reduced energy consumption – saving both money and the environment!

SFX PSUs come with a host of features making them the ideal choice for anyone who wants a powerful yet petite PC setup without compromising performance. Whether you’ve got a mini ITX build or want to maximize your workspace in Micro ATX form factor, an SFX PSU has all the essentials needed while keeping everything neat and tidy!

ATX vs SFX: Compatibility

Compatibility’s key when selecting a PSU, so make sure it’ll work with your case, motherboard, and components – no matter how small or large.

The size of the PSU will determine if it fits in your system’s chassis, while its main connector needs to match that of your motherboard.

Additionally, you need to ensure that the PSU has enough CPU and GPU connectors for the CPU and GPU, as well as enough peripheral connectors for storage devices, fans, and other components:

  • Make sure the size of the PSU fits in your system’s chassis
  • Check if the main connector matches that of your motherboard
  • Ensure there are enough CPU & GPU connectors for both components
  • Confirm there are sufficient peripheral connectors for storage devices & fans
  • Compare specifications between all components & PSU to ensure they match

It’s important to prioritize compatibility when selecting a power supply unit so you can be assured you’re getting exactly what you need.

ATX units tend to provide more power than SFX models but may require additional clearance depending on their wattage at times. It’s up to you which one works best depending on your preferences.

Ultimately, take into consideration what kind of wattage is required by your system along with all other compatibility requirements before making a purchase decision.

Interesting Read: Should My PSU Fan Be Up or Down?

ATX vs SFX: Cable length

You could be missing out on some extra space if you don’t check the cable lengths of your SFX PSU – they may require a few extensions to fit in bigger cases, so make sure you double-check before investing in one!

Since SFX PSUs are designed to save on space, their cables are usually shorter than those found in ATX PSUs. This can be a problem in larger PC cases, where components may be spread out and require longer cables for proper setup.

In order to avoid this issue, it’s important to consider the following when looking into an SFX PSU:

  • Check the case dimensions and cable lengths of your components against the length of the cables provided with your chosen SFX PSU.
  • Investing in a few extra cable extensions might not break the bank but can give you that extra breathing room needed for full functionality without creating unnecessary clutter.
  • Don’t forget to factor in potential fan noise if using an SFX PSU inside an ATX PC case – although these units have higher wattages now they may still run louder than ATX ones due to smaller fans and heat output from cramming components into such a small box.

Choosing between an ATX or SFX power supply for your build ultimately comes down to personal preference – what works best for one person might not work as well for another depending on budget, performance needs, space constraints, etc.

As long as you know what you’re getting yourself into and keep all these considerations in mind when making your selection, you should end up with something that suits your needs!

Can you use an SFX power supply (PSU) inside an ATX PC case?

The small size of an SFX PSU may open up some much-needed room for your components, but make sure it’ll fit in your system’s chassis and provide the necessary power – otherwise you could be left disappointed!

Generally, the larger ATX cases should have no problem fitting an SFX PSU. However, if you’re using a smaller case such as ITX or micro-ATX, then it’s important to check both the manufacturer’s specifications as well as whether or not you need any adapter to install the PSU properly.

It’s also worth noting that most SFX units are fully modular which allows you to pick and choose what cables to use while reducing cable clutter.

When considering an SFX PSU for your build, remember that they are electrically the same as regular PSUs so there should be no worries about them providing enough power for all of your components. Furthermore, many modern SFX PSUs can come with 80+ ratings with 88-92% efficiency and wattage increases up to 1000W – so electrical performance isn’t necessarily ‘worse’ anymore compared to their ATX counterparts.

SFX PSUs may have higher prices due to cramming components into a smaller box and noise levels due to smaller fans; however, if extra space is preferred and potential fan noise isn’t a concern then these units shouldn’t be overlooked.

With its small form factor but high wattages available, investing in an SFX PSU could be just what you need for your dream gaming PC set-up!


I’ve compared the features and benefits of ATX vs. SFX PSUs, and it’s clear that SFX PSUs offer a great solution for those looking for a powerful gaming set-up in a small form factor case.

They are more compact than traditional ATX PSUs, allowing for greater flexibility when selecting parts. They also come with modular cables, which can reduce cable clutter and make installation easier.

All in all, an SFX PSU is a great choice for any small form factor build!

I am a computer engineer holding a bachelor's degree in Computer Science, complemented by a Master's in Business Administration from University of Strathclyde, Scotland. I currently work as a Senior IT Consultant in Melbourne, Australia. With over 15 years of...