ATX vs SFX vs SFX-L: Power Supply Form Factors and Sizes Explained

Introduction

The best thing that happened for PC power supply was standardization. It made it convenient for consumers to pick the form factors that best suit their requirements. In the earlier days of personal computers, the 1000W power supply we have today would be the size of a shoe box. The technology evolved with the introduction of  GaN (Gallium Nitride), which drastically reduced the power supply size. Now they can fit inside a small form factor PC case while providing the power required to run powerful top-tier hardware.

This article will explain the three main form factors, ATX, SFX, and SFX-L, in detail. We will cover aspects like dimension, power, and connectivity. To ensure that our readers have a clear idea of these power supplies, we will start with the basics of power supply form factors.

What are PC Power Supply Form Factors?

PC power supply form factors were created to ensure predictability. Which means ensuring that a power supply from one brand is fully compatible with the motherboard and PC case from other brands. Intel, in July 1995, standardized the following key elements of power supplies to ensure cross-platform compatibility:

• Height and Width: The two dimensions were fixed for power supplies following the standard. It ensures that the PC power supply slides comfortably across multiple PC cases' mounting brackets.
• Screw Pattern: The screw patterns were fixed to ensure that all PC cases would align perfectly with the power supply mounting positions. A 2010 ATX PSU will still fit a PC case from 2026.
• Connector: All the connector shapes were standardized so that there is no chance of accidentally plugging in the wrong connectors. It also helps standardize hardware component connectors.

The standards that are now widely manufactured and used in various applications are ATX, SFX, and SFX-L. We will explore each one in separate upcoming sections.

ATX Power Supply Form Factor

Advanced Technology eXtended (ATX) is the most common and highly valued form factor. Owing to the GaN technology, it became possible to fit powerful components within the confined space of an ATX PSU. While we talked about the generic approach of form factors, let's specify what defines an ATX power supply as per Intel.

Geometrical Constraint

The physical rule that defines the ATX power supply is its fixed 150 x 86 mm dimensions. Here, 150 mm is the width, while 86 mm is the height. Across all brands and makes of ATX PSUs, these dimensions will remain fixed. The length is where the designer is allowed a margin to incorporate their electronics. Some high-capacity PSUs need greater depth due to larger capacitors and modular cables. The depth can be anything between 140 mm and 230 mm or beyond.

Cooling Advantage

Owing to the spacious interior of the ATX power supply, the manufacturer can fit a larger fan inside the PSU enclosure. Typically, the 120 or 140mm diameter fans can fit perfectly inside the ATX power supply form factor. The large fan size allows more air flow with lower RPM. It drastically reduces noise levels.

Cable Management

PSUs come in fixed cable, semi-modular, or fully modular configurations for cable management. Modern high-end ATX PSUs come with fully modular cable management, which allows users to plug and unplug cables as required. It reduces the clutter inside the PC case, making it cooler and aesthetically pleasing.

The recent development in power supplies is the use of ATX 3.1 and the 12V-2x6 connector. PC power supply manufacturers use it in all form factors, but its application to ATX power supplies is vital. As they are the most powerful and provide the raw power required by modern GPUs without melting the connector. Its predecessor, 12VHPWR, suffered from connector melting issues with modern, powerful GPUs.

SFX Power Supply Form Factor

Moving to compact form factors, the first one is SFX (Small Form Factor eXtended). It is generally selected by PC builders who are aiming for compact PC cases with a smaller footprint. GaN-based components are replacing the older silicon MOSFETs and diodes. These small form factor PSUs have become surprisingly powerful.

Compact Size

A SFX power supply has a smaller footprint than standard ATX units. They have fixed dimensions of 125 mm width x 63.5 mm height x 100 mm depth. They are specifically designed to fit into mini-ITX and SFF (Small Form Factor) cases.

Power Outputs

Manufacturers of PC cases are pushing their design limits to create compact dimensions. They mimic dimensions of gaming consoles, allowing computers to be used as HTPCs with a compact footprint. However, do not let the small dimensions throw you off. They are incredibly powerful and can support 1000W power delivery required for the most powerful GPUs and CPUs with ease.

Noise Considerations

The compact size does come with a drawback. Pushing such a high number of electrons to the PC components does lead to heat generation. Most PC users prefer the 80 Plus Gold-certified PSUs. Which means they still need to reject 10% of the power they draw from the wall socket as heat. At peak loads, the fan inside the PSU can get loud due to its small size.

Smart Cable and Fitting

These SFX form factor PSUs come with cables of shorter length as compared to other larger PSUs. They are packaged deliberately by the PSU manufacturer to avoid cable clutter, which can affect performance in small PC enclosures.

PSU manufacturers provide brackets that allow SFX power supplies to fit inside a larger ATX PC case. Users utilize SFX PSUs in larger ATX-based PC cases to allow space for installation of custom cooling loops and ornaments to enhance aesthetics.

SFX-L Power Supply Form Factor

SFX-L stands for Small Form Factor eXtended - Long. It is the extension of SFX and bridges the gap between a large and a miniature PSU. IPC case manufacturers utilize their slightly larger dimensions to their advantage.

Physical Size

The width and height of the SFX-L are similar to those of the SFX. It means the mounting holes will still align perfectly with the PC case for SFX PSUs. However, the room inside the PC case along the length should be 130 mm. The extra 30 mm allows the PC power supply manufacturer to add electronics to enhance its power supply capability.

Cooling and Noise

The key reason why SFX-L power supplies were introduced was the noise levels. SFX power supplies couldn't fit a reasonably sized fan unit. It made ensuring low temperatures challenging for manufacturers. With the increased length, instead of fitting a tiny 92 mm fan, these PSUs can fit a 120 mm fan. These run at lower RPMs and ensure better cooling in comparison to the same power PSU with the SFX form factor.

High Power and Smart Cabling

The better cooling allowed engineers to develop higher power PSUs with fully modular cables. High-end gaming PCs require a 650W to 1000W+ power supply.

Head to Head Comparison ATX vs SFX vs SFX-L

To help our readers capture the comparison at a glance, we have converted all the information into tabular form:

Conclusion

The three form factors: ATX, SFX, and SFX-L are now widely available in the market. Users can pick the ATX for spacious PC cases, SFX for compact PC cases with low power requirements, and SFX-L for miniature high-end PC cases. Each of them offers its unique dimensional advantages.

If you are looking for a manufacturer that produces 80 Plus and Cybenetics certified power supply units for PC, then consider ESGAMING. Founded in 2017, ESGAMING has quickly become a recognized emerging brand in high-performance computer components and accessories. From PC cases and power supplies to cooling systems, ESGAMING is dedicated to delivering creative, reliable, and well-crafted E-sport solutions for gamers, creators, and PC builders around the world.

For more information, visit www.esgamingpc.com