Ultimate Guide to Computer Power Supply: ATX, SFX, TFX, & EPS

PC building is an exciting process. You build a powerful PC with highly compatible components and gain immense knowledge in the process. When selecting a power supply unit (PSU) for the PC, you might come across multiple terms, including ATX, SFX, TFX, and EPS. These represent the physical dimensions of the PSU. Ensuring that you select the correct dimension is critical for PC building, as it needs to physically fit and align with the mounting holes of the PC case.

Whether you build a powerful computer for professional work or a small HTPC (Home Theatre PC) for a compact performance rig, you will need to select the right form factor for the computer power supply. Selecting a reputable PC power supply manufacturer means you will have a standardized approach to manufacturing and key certifications for reliability. Let's quickly cover why power conversion matters, and then we can understand the depths of the key form factors.

Mechanics of Power Supply

Before we dive deep into each type of power supply lets understand the key features of a power supply. These can vary between these power supplies owing to their physical dimensions.

• AC to DC Current: The key function of a power supply is to convert the high-voltage wall outlet AC current into low voltage DC current requirement by PC components. It does that using a transformer and a rectifier circuit. Collectively, they convert a sinusoidal current into pulsating DC on which your GPU, CPU, RAM, Storage Drives, and other components work.

• Filteration: There are other components besides the transformer that clean up the current supply, one of which is the capacitor. You need a high-quality capacitor to have a long-lasting PSU. The most popular are the black Japanese capacitors. It helps prevent the unexpected shutdown and freezing of the PC.

• Rail Distribution: The power after conversion needs to be distributed into different voltage levels. The biggest power goes through the 12V rail to the CPUs and GPUs that consume the most power. The 5V and 3.3V rails are for smaller accessories and RAM.

• Voltage Stability: Advance power supplies use DC to DC converters design. These networks that power never fluctuate and maintain a voltage level within 1% margin. These ensure that your system runs at peak performance.

• Active Power Factor Correction (PFC): It's a built-in technology that enhances power efficiency and cuts down electrical waste. Power correction is usually a hallmark of premium PSU suppliers.
• Hold Up Time: To keep the computers running, we need to have a hold-up time of 21 milliseconds. It means that the PC runs stable even when the split-second blinks or drops in home electricity occur due to power grid issues.

• Zero Fan Mode: As PSUs are becoming more efficient, they create less heat. An 80 Plus certified PSU will have atleast 80% efficiency, only a small amount of heat is generated, which can be removed using a fan at peak loads. However, in idle mode or low load conditions, the fan does not even need to run, and it stops at zero RPM, improving the efficiency of the system.

ATX: The Desktop Standard

Physical Dimension

These are the most common types of PSU physical size and shape for desktop power supplies. The Advanced Technology eXtended form factor typically has a width of 150mm and a height of 86mm. However, the depth is not fixed by any standard. It can be between 140mm and 220mm long. It mostly depends on the power supplying wattage of the PSU, which can be between 300W to extraordinary 1600W.

ATX 3.1 and PCIe 5.1

Modern ATX power supplies come with ATX 3.1 and PCIe 5.1 readiness. These are particularly vital for high-power-consuming GPUs like the Nvidia RTX 5090 or AMD Radeon RX 9070 XT. It means if the PSU has these features, it can handle 2x its official PSU rating for short intervals, typically in the range of 100ms.

Almost all high-end ATX power supplies come with the 12V-2x6 connectivity that supplies an enormous 600W. These are required for the next-gen graphics card.

Thermals and Wire Layout

As there is sufficient space, ATX power supplies come with 120mm or 140mm FDB cooling fans. Owing to their size, they can keep the PSU cool under load to maintain its efficiency. A fluid dynamic bearing fan can last up to 100,000 hours of continuous operation. A top-tier computer power supply also offers digital control for hybrid fan mode. These allow the user to select how the fan reacts to changing temperature conditions.

The spacious physical dimensions also allow side-mounted cabling that is readily available for ATX power supplies. These make cable management convenient for a specific chassis layout.

SFX & SFX-L: Power for Compact Builds

For Compact PC Cases

For PC cases that have space constraints, SFX offers the most miniature enclosures. They are 125mm wide, 63.5 mm high, and 100 mm deep. Unlike ATX, these have a fixed depth, which makes them ideal for compact PC case manufacturers. They can ensure a fixed space in the PC case to ensure that the PSU always fits.

Another version that is slightly longer is the SFX-L, which has a depth of 130mm. One would question why the PPSU is divided into different lengths. It's because sometimes SFX does not have enough space to allow high-wattage electronics. You need longer versions to deliver at par with ATX power supplies.

Power Delivery and Parts

Small dimensions did not stop manufacturers from producing powerful PSUs. An SFX-L model can reach up to 1300W. It means that the power density is amazing, 26.8W for every cubic inch of PSU space. Pushing this much power requires the minaturization of internal electronics. It means that the layout has to be precise with proper routing of cool air. Due to the intricate engineering details, the cost is higher than a similar wattage ATX form factor.

Fitting in Big Cases

Large PC cases have ample space to fit in any type of power supply. However, some enthusiasts may want to gain a little extra room in their chassis. For that, they can use an adapter bracket or ATX mounting brackets to fit an SFX or SFX-L power supply into their PC unit. It allows more air to move through the PSU with already efficiency components.

TFX & EPS: Specialized Workflow Standards

Slim Computers or Reliability

The TFX means Thin Form Factor PSU. These are exactly 175mm deep, 85mm wide, and 65mm high. These are targeted for short and flat computers that are typically used in the office. A low-profile PC that works reliably while ensuring small workstation space occupation.

The EPS (Entry Level Power Supply) is the modified version of the standard ATX power supply. These are designed for high-performance workstations and servers that require 24/7 operation. They need premium electronic components to ensure reliable function.

Powering Multiple CPUs

The heavy-duty EPS power supplies come wan with12V specification. It means they come with an extra 8-wire power cable for the CPU. Which means they will have (8+8), which is necessary for motherboards that support dual physical CPU installation.

As these workstation PCs are for professional use, they need to ensure proper voltage regulation. Data corruption on server PCs can not be tolerated, nor any break-in to a complex graphics or video rendering task.

Crucial System Requirements

For mission-critical servers like the ones used by NASA, they need to follow the SSI EPS specification. The rules that define the specification require rigorous testing of the design to make sure the electricity is perfectly balanced across all the rails.

PSU Specification Comparison

Conclusion

For a regular PC user with a mid-tower PC case, ATX is the ideal computer power supply. They offer the best performance-to-price ratio with sufficient power and efficiency. For compact chassis owners, SFX or SFX-L is the right choice. In the case of server-grade configurations, EPS offers the most stable power supply. Overall, the choice is dependent on the user. Manufacturers like ESGAMING ensure that they provide the best efficiency and stability, irrespective of the PSU form factor.

For gamers who want a high efficiency, standardized, and tested PSUs, consider ESGAMING.