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The PC Power Supply Guide for the Masses

  1. Introduction
  2. PSU Abbreviations and Glossary
  3. Connectors used in a PC Power Supply
  4. PSU cables: Non-Modular, Modular and the middle-ground!
  5. Power Supply Labels
  6. Power Supply Form-Factor- ATX12V
  7. Power Supply Form-Factor- SFX12V
  8. Basic requirements of a power supply
  9. Facts about 80 Plus Certification
  10. Protection Circuits and Features
  11. List of Power Supplies, OEM and Review Links
  12. Common PC Power Supply Myths
  13. Resource Links and References
  14. View All

One of the most important points for a power supply is the form-factor. Most commonly used form-factors is the ATX design, but there are certain designs made for specific uses and form-factor systems like PICO-ATX.

For the sake of keeping it relevant, we will be talking about ATX and SFX. Though ATX is what almost all DIY PC builders would get, SFX are reserved for small form-factor PCs. There are other types, which is usually for prebuilt systems and servers.

The types of PC power supplies are as follows:


ATX is the form-factor that most people will use with their PCs. This was originally introduced by Intel along with changes for their motherboard in 1996. At first, the main motherboard power connector was 20-pin, and it came with two voltages- +3.3v and +5VSB. These two voltages enabled the systems to turn on the system without pressing the switch on the PC case (provided its enabled in your BIOS) by pressing the key on the keyboard or mouse. This function is called “Power-on Time”.

Over the years, there have been newer revisions of the ATX specification to meet the requirements of new-age hardware components that users require and desire. Over the revision, power supplies came with extra cabling for graphic cards, 24-pin motherboard connectors, SATA power connectors and so on. As of now, ATX12V 2.x revision is what we’re getting which introduced 24-pin connector and PCIe power connector.

ATX12V form factor has two types of venting design- Top Venting and a non- top venting form-factor.

top venting

Top venting is where you have a vent/fan at the base and fan/vent on the AC plug/switch area.

Older power supplies based on top-vent cooling used to have 80-92mm fans on the AC plug and keep a vent on the base. But with additional components and features added to meet higher quality standards, it needed equivalent cooling. The fans were installed on the base, and it enabled the manufacturers to install either 120 or 140mm fan. This is how ATX most power supplies are, but there are non- top vents too. This has become the commonly used design since power supplies are now usually mounted at the base of a PC Case.

non top venting

In a case of non- top vents, There’s a fan installed towards the AC Plug area and the wire harness area is vented.

For such power supplies, there are certain areas of the casing where the vents are provided. However, the only restriction is such design is that you can only accommodate 80mm fan.


  1. Koolest ripper guide to What is and what is not on SMPS!
    Thanks for adding those SMPS suggestions! 🙂

  2. Much appreciated!

    I plan on putting more guides per component so that many people from newbies to regular users can understand “what is” and “what is not” for many components to help them make better purchase decisions! This way, we can guide even the newest of end users to understand whenever they read our reviews!

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