Explore the key features of an ATX PSU and additional factors that will power your PC’s components today and in the years ahead. 

What does an ATX power supply mean?

ATX PSU (Advanced Technology eXtended) is a widely used standard for PC components – motherboards, PC cases, power supplies, etc. It was designed to make sure that all the components inside a computer can work together smoothly, even if they’re made by different manufacturers. It’s a versatile component for your PC that provides all the inner parts with power. 

In simple terms, it powers the entire system unit. The standard defines the size of the power supply (usually around 150 mm × 86 mm × 140 mm), where the mounting holes should be, and how the connectors are placed. This helps ensure that different parts fit and connect properly. Like pieces of a puzzle.

The ATX PSU delivers power through a main 20- or 24-pin connector to the motherboard, along with additional connectors: EPS for the CPU, SATA for drives, PCIe for graphics cards, and Molex for peripheral devices.

Thanks to this standard, you get a stable and reliable power supply, support for turning the PC on/off via software, and compatibility with modern hardware. All in one compact unit.

Where is an ATX PSU used?

The ATX power supply is mainly used to power desktop computer components. It’s compatible with both standard full-sized PCs and more compact builds. Like ATX, Micro ATX or Mini ITX. Basically, you’ll often find it in setups built by gamers or enthusiasts who like to upgrade and tweak their computers for better performance. It’s a perfect choice to improve both existing and in-the-making PCs.

It’s also a great fit for DIY projects. Let’s say when you want to build your own system from scratch. An ATX PSU, the heart of your system, ensures that all your components, such as the motherboard, graphics card, and case fans, receive stable and reliable power.

More powerful versions of ATX power supplies, which include 12V rails and extra connectors, are used in high-performance and server-grade systems. For example, with multiple drives, multiprocessors, or GPU storage, powering SMP/multiprocessor systems and GPU accelerators for AI. 

And it doesn’t stop there. ATX PSUs are also used on an industrial level. There are specialized industrial ATX units ranging from 100 to well over 3000 watts, built to handle tasks in automation, embedded systems, and powering machinery that needs more juice than a standard PC.

How does an ATX PSU differ from other form factors (SFX, TFX, Flex ATX)?

There are basic indicators that distinguish a standard ATX from other PSUs.

This data will help you pick the PC productivity option that’s right for you.

What are the standard dimensions of an ATX power supply?

ATX PSUs have the following standard dimensions that you should consider before working with them:

PSU Width: 150 mm.

PSU Height: 86 mm.

PSU Depth: 140-230 mm. It always depends on the model. Sometimes you can find sizes of 160, 180, or even 200–230 mm. They’re for more powerful, modular models.

Clear standards make sure the power supply works with all your PC components.

What components does an ATX PSU power in a typical PC build?

In most PC builds, the ATX power supply unit (PSU) powers the key components that keep everything running smoothly.

First up is the motherboard. It usually gets its power through a 24-pin connector. Also, it supplies energy to the RAM, chipset, USB ports, and expansion slots.

Next is the processor (CPU). It receives power through a 4- or 8-pin ATX12V or EPS connector. It feeds the voltage regulator on the motherboard.

The ATX PSU also powers the graphics card (GPU). It typically connects through one or more 6+2-pin PCIe cables as well as 12VHPWR (ATX 3.0) or 12V-2×6 (ATX 3.1) cables for most recent GPUs. Storage devices (like SSDs or HDDs) and other peripherals usually connect via SATA power cables. 

System fans are primarily powered directly by the motherboard. However, if connected through USB hubs or dedicated fan controllers, they may instead draw power via Molex or SATA cables.

So, the ATX PSU is the heart of your system, delivering power to all the right places and making sure everything works together reliably, around the clock.

How important is wattage when choosing an ATX PSU?

It has a high level of importance in this case. A PSU’s wattage is one of the most important things to consider. Why so? Because your power supply needs to cover the energy demands of all your components – the CPU, GPU, motherboard, storage, and other parts. Knowing the index you need, you choose the right PSU for your system that will pay off. 

The next important thing. Choosing a power supply with a 20-30% reserve will ensure the power supply lasts longer. This gives you some breathing room and protects the system from sudden drops in performance or unexpected shutdowns. As experts in this area, we also recommend doing so. 

If the power supply doesn’t provide enough wattage, your PC might crash, restart unexpectedly, or fail to turn on at all. Simply because it can’t feed enough energy to all components. But going too far in the other direction isn’t helpful either. An overly powerful PSU doesn’t make your computer run better; it just adds to your electricity bill and might end up being a waste of money. “More” doesn’t always mean “smarter.”

That’s why the best choice is a high-quality, reliable PSU that slightly exceeds your system’s needs. For example, an ATX 3.1 power supply unit with modern features and efficiency standards would be a solid investment for long-term stability and smooth performance.

What connectors are typically included in an ATX PSU?

There’s a set of standard connectors on an ATX power supply that deliver stable power to all your PC’s components. The following list it’s a standard for ATX PSU units. 

1. The 24-pin ATX connector: powers the motherboard, chipset, RAM, USB ports, and expansion slots. 
2. A separate ATX12V or EPS connector: for the processor.
3. PCIe cables: for the video card. If you’re working with a high-end GPU, it may require a 16-pin 12VHPWR (ATX 3.0) or 12V-2×6 (ATX 3.1) connector instead. 
4. 15-pin SATA connectors: for storage devices like SSDs and HDDs. 
5. And if you’re using older hard drives, fans, or some peripherals, the classic 4-pin Molex connectors still come in handy.

What is the role of the 80 PLUS® certification in ATX power supplies?

80 PLUS® certification shows how efficiently a power supply unit uses electricity. In short, it tells you whether the PSU is wasting energy or putting it to good use. It works even better when you choose one that fits your system’s energy needs.

A certified PSU won’t overheat or run loudly because it doesn’t waste energy, it only uses what’s needed to power your tasks. Less wasted energy means less heat, and that means quieter fans and a longer lifespan for the unit itself. It works like the clock and lets you utilize your PC in the way you really need. 

There are Bronze, Silver, Gold, Platinum, and Titanium certifications. It’s pretty simple to distinguish them. The higher the level, the more efficient the PSU. For most work or gaming setups, Gold is the “go-to” solution over Bronze or Platinum. In other cases, choose more powerful options. 

So, when you see a PSU marked as “80 PLUS® Gold” or “Titanium,” it’s a strong indicator of energy efficiency, which often goes hand-in-hand with better-quality components and design.

How do modular, semi-modular, and non-modular ATX PSUs compare?

Here are the differences between modular, semi-modular, and non-modular ATX power supplies in simple terms. It may help you choose the one that fits your current needs while working on a PC.

Modular
With this type, all the cables are detachable. You only plug in the ones you need, which helps keep the inside of your case neat and tidy. It’s easier to build and great for airflow. Yes, it costs more, but the convenience is often worth it, especially if you build PCs regularly or care about cable management. It’s a perfect choice for that.

Semi-modular
Here, some essential cables (like the one for the motherboard) are already attached. But the rest of them you can add as needed. It gives you a balance: a cleaner setup than non-modular, but without the higher price of a fully modular PSU. It’s a solid middle-ground choice for most users.

Non-modular
All cables are permanently attached and cannot be disconnected. It’s a good option if you don’t plan to tinker with your build much. Just for work without any updates.

The general idea – Go modular for flexibility, semi-modular for a smart balance, and non-modular if you just need something simple that works.

Can an ATX PSU be used in any PC case? 

Power supply units follow standard dimensions (150 mm width, 86 mm height, and 140 to 230 mm depth). The mounting holes are also standardized, so these power supplies are compatible with most ATX and micro-ATX cases. As a rule, they also have the same characteristics. That is why, in most cases, they are perfectly fit for ATX PSUs. 

Typically, an ATX PSU fits just fine in a micro-ATX case because they share the same standard. The only detail that might cause trouble is the depth of the PSU. Some models, especially powerful or ATX 3.1 power supply units, can be longer than usual.

The good news is that ATX 3.1 PSUs still fit in around 90% of standard ATX and mATX cases without issues. You just need to double-check the available space inside your case, especially if it has a tight layout or a shroud at the bottom. Compare the depth of the PSU with the clearance in your case, and you’re good to go.

What should you consider to buy the best ATX 3.1 PSU in 2025?

It would be enough to check the following points. 

12V-2×6 connector
This is the key update in ATX 3.1. Unlike older versions, this connector has a safer design with longer power and shorter signal contacts. It reduces the risk of overheating and poor connections, especially with high-end GPUs.

Power output
If you’re building a PC with a powerful graphics card or planning future upgrades, go for a PSU with at least 750–850W. As a practice shows, while 650W might be enough for some builds, having a 20–30% power reserve helps the unit last longer and handle peak loads better.

80 PLUS® certification
Aim for Gold, Platinum, or Titanium-rated models. These are more energy-efficient, generate less heat, and usually run quieter. It’s a win-win option for performance and comfort.

Compatibility and upgrades
Make sure the PSU fits your case, especially the depth (some models go up to 230 mm). If you expect to upgrade your GPU later, it’s smart to choose a PSU that already supports the new 12V-2×6 standard.

Choosing the best ATX 3.1 PSU from the Seasonic FOCUS or PRIME Series, your system gets stable power, quiet operation, and upgrade flexibility. Everything a modern PC build needs.

Conclusions

An ATX PSU is the heart of your system and a key player in your PC’s stability, protecting it from crashes, overloads, and unnecessary stress. When you understand how it works and what your components actually need, it becomes much easier to choose the right one. A well-matched power supply won’t just support your tasks – it’ll quietly and confidently power your entire system.