A Complete Guide to PC Power Supplies: ATX, SFX, TFX, & EPS Types
So you finally have a PC build with the right CPU, cooling system, graphics card, motherboard, RAM, storage devices, PC case, and more. The next step is to power all your components with a PC power supply, but you come across these overwhelming terms like ATX, SFX, TFX & EPS. If you want to know what these terms are and how to select the proper PSU for your PC, you are at the right place.
In this guide, we will cover all the key aspects to consider before purchasing a PC power supply. Moreover, it will address why PSU type matters and how it impacts the PC configuration, PSU applications, performance, and reliability. Evaluating physical dimensions is the first step in power supplies, but all other parameters are equally important. We aim to explain all the crucial aspects of power supply so that our readers can find the perfect match for their PC configuration.
Factors to Consider in PC Power Supplies
As a buyer of a PC power supply, you need to understand all the specifications and features of a modern PSU. Owing to the rapid change in technologies, they are ever evolving, particularly in efficiency and safety. Power supply is a key component in a PC. A badly selected power supply can lead to BSOD, underperforming hardware, and sudden shutdowns. In the worst case, it may even lead to hardware component failure. Therefore, here are factors to consider when selecting an ideal PC power supply:
Form Factor
The size of the power supply can also be called form factor. It determines the size of the power supply and its compatibility with the computer's PC case. ATX, SFX, TFX, and EPS are all form factors. They determine the physical dimension of the power supply, which can directly impact its ability to offer a number of connections and power capacity. Moreover, PC cases come with mounting holes that should match the casing. We will dive deeper into the form factors in the next section.
Main Takeaway: As a buyer, you need to evaluate form factor compatibility with your PC case carefully.
Wattage
After you have the right form factor for the PC case, you can decide on the wattage supply capability of the PSU. If you are building a new PC, then analyze all the components in your build, and mainly the components that consume the most power. Look for wattage consumption for each element in their specification, and add all the wattages together; it will give you the required PSU wattage. Alternatively, you can search online for power supply calculators for ease of calculation.
Main Takeaway: Add the power requirement of all main PC components, e.g, CPU, GPU, RAM, Cooling System, Motherboard, Storage Devices, etc. It will give you the required PSU wattage.
Safety Overhead
You will always need some power margin for the PC components. There can be times when these components may demand higher power from the power supply. Those peaks should also be considered when selecting wattage for a PC. Usually, experts recommend using at least 20% to 30% margin in the calculated total maximum power draw that you calculated in the wattage section.
Efficiency Rating
Another key factor to consider is the efficiency rating. It will determine how much energy your computer consumes to power all the PC components. Suppose you purchase a 600W power supply after calculating the wattage of the power supply and adding safety overhead. Your PSU will consume 750W from the power outlet if it has an 80% efficiency. Higher efficiency means lower power consumption and energy bills.
That's why you need certification of efficiency, like:
- 80 PLUS
- Cybenetics
Modularity
It is the ability of the power supply unit to attach and detach cables running out from it to PC components. There are mainly three types of PSU in terms of modularity: fully modular, semi-modular, and non-modular. Having a PSU of any form factor amongst the four mentioned in the title of this guide, modularity can offer convenience. These can reduce the cable clutter and make sure the cables are aesthetically compatible with the remaining setup. You can choose different aftermarket cables to go with the PC.
Connectors
These are the connectors at the end of the cable that supply power to your computer hardware components. Therefore, their compatibility with the PC components you choose in your build is key. The motherboard connector is common in modern PSUs, but the other connectors can change. Here is their list:
- 24-pin ATX Connector (often 20+4 pin)
- CPU / EPS Connector (4-pin, 8-pin, or 4+4 pin)
- PCIe Power Connector (6-pin, 8-pin, or 6+2 pin)
- 12VHPWR / 12V-2x6 Connector (16-pin)
- SATA Power Connector (15-pin)
- Molex Connector (4-pin)
Main Takeaway: Analyze the number of connectors you need to power your computers. Then make sure the PSU you pick, irrespective of the form factor, offers the connectors.
Safety Features
Here are some self-explanatory safety features you need in your PSU to protect your PC and components:
- Over-Voltage Protection - OVP
- Under-Voltage Protection - UVP
- Over-Power Protection - OPP
- Short-Circuit Protection - SC
- Over-Current Protection - OCP
- Over-Temperature Protection - OTP
Types of Power Supplies
Now, let's move to our main segment of the article where we discuss the form factors in depth. As we now know, form factor is directly related to its physical dimensions, which can indirectly impact its connections, wattage, and cooling mechanism. Let's begin understanding them one by one:
1. ATX (Advanced Technology eXtended)
The ATX power supply is the most standard go-to option for most PC builders. It offers the most versatile options with power delivery capability. Their standard dimensions are usually the width and height (150mm x 86mm). However, the depth can vary significantly between 140mm and 230mm.
Features
- Noise Levels: Due to their size, they can house a bigger fan for cooling, typically a 120mm or 135mm. It results in better cooling performance and lower noise levels.
- +12V Rail: Modern PSUs supply almost 80 to 90% of their power through the +12V rail, and ATX form factor features them. They would typically offer the modern 12VHPWR / 12V-2x6 to supply current to the power-hungry graphics cards.
Usage
These are most popular amongst standard desktop PCs, high-gaming rigs, and builds where there are no space constraints.
2. SFX (Small Form Factor eXtended)
As the name suggests, the small form factor eXtended is meant for PC cases with a form factor of Mini-ITX or SFF (Small Form Factor). They typically come in a standard 125mm (Width)×63.5mm (Height)×100mm (Depth) dimensions. However, these can vary depending on the manufacturer's design. The mounting holes will still align as long as the PC case and PSU are both for the same form factor.
Features
- SFX-L: It is another slightly different power supply form factor that has the same width and height as the SFX PSU. However, it has a greater depth of 30mm, allowing for bigger fans and cooler running operation.
- Space Efficiency: Modern gaming or high-wattage SFX PSUs will offer very high power density. The miniaturization of PSU components while using the highest quality components can lead to better power output. However, these components can increase the price tag. They are usually fully modular to allow space efficiency in cable management.
Usage
Ideal for premium micro gaming PC builds or office use PCs with low power consumption.
3. TFX (Thin Form Factor eXtended)
A further narrower form factor, which is popular in miniature PC builds, is the TFX. Their standard dimensions are 85mm (Width)×64mm (Height)×175mm (Depth). The thinner width and more extended depth allow the power supply to fit in small enclosures conveniently with space efficiency.
Features
- Unique Dimensions: These power supplies have unique dimensions, often tailored to suit custom PC enclosures. Finding TFX can be challenging as they are less common and do not offer high-end gaming performance.
- Higher Noise: Due to the tighter configuration and smaller fans, high-end power supplies with larger wattage can create louder noise under operation.
Usage
Ultra-Slim PC enclosures, proprietary designs, small form factor office computers, or home theatre personal computer (HTPC)
4. EPS (Entry-Level Power Supply Specification)
The physical size of the EPS power supply is not different from the ATX form factor. However, they indicate highly reliable power output suitable for a server/workstation. Most users will not find them relevant unless they are building a server PC where reliability supersedes efficiency or space efficiency.
Features
- Unique Standard: These PSUs adhere to the EPS12V standard, which was developed by the Server System Infrastructure (SSI) forum. They have more robust CPU connectors: 8-pin or dual 8-pin (4+4-pin or 8+8-pin) +12V connection. These can handle dual CPU motherboards and high-end server PC components.
- 24/7 Operation: Owing to their reliable components, they are designed to work 24/7 without exceeding their operational temperature limit or lowering the product's operational life.
Usage
High-performance workstations, server builds, and enthusiast-grade motherboards that require multiple or dedicated CPU power inputs.
Conclusion: Which PSU Type is Best?
Labeling a particular PSU as the best can be misleading, as the user decides which suits their specific application. By following the guide, PC builders can find the right and most compatible power supply. ATX, SFX, TFX, and EPS are all form factors that have different dimensions and purposes. Most users will opt for the ATX power supply unit with the modular connectors and at least 80 PLUS certification. While enthusiasts or unique builds may also feature SFX or TFX builds. For server PCs, EPS suppliers are ideal for their standard approach to 24/7 working operation.
If you are looking for high-end gaming PC power supplies with different form factors, consider visiting the ESGAMING website. They offer a variety with premium features that most gamers would deem necessary, like RGB lighting, modularity, wattage, safety features, and efficiency rating. Visit their website to learn more!