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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

24-Pin Connector:

Major part of the motherboard takes power from the 24-pin Motherboard connector. Some power supplies label them as “20+4” ATX pins. This is because very old motherboards use 20-pins, and if any reason you need to use modern power supplies on much older systems, you can detach the “+4 connector” from the rest of the connectors.

As per ATX power supply specifications, they haven’t been physical changes. But you should know that power supplies that we’ve been getting has the 20th pin with no wire. Don’t be alarmed. This is because this requirement was phased out years ago, since ATX12V v2.01 spec days.

To ensure proper installation, there’s a clip on the PSU side of the connector, which attaches firmly on the motherboards once it’s installed.

4-pin CPU Connector:

It’s a 4 pin connector which powers the area of the motherboard dedicated for processors and its components. It’s also a vital connector that provides power to the processor and must be connected at all times.

8-pin CPU Connector:

It has the same purpose as the ATX12v (4-pin CPU) connector. But it gives either more power or deliver power efficiently via the 8-pin connector.

Almost all power supply manufacturers use 4+4 ATX connector so that it can be compatible with both 4-pin and 8-pin connector on the motherboards. Most good reputed power supplies can split EPs 12v connector into 2 atx12v connector. Other either have one EPS 12v connector or ATX 12v connector. Some motherboards come with 8 pin+ addition 2-4 pin. This usually a feature in motherboards made for extreme overclocking. But this is redundant for those users who aren’t into extreme overclocking and use LN2 as a means to cool down the processor.

Just like the 20+4 pin, these also have detachable “+4” connector and each have clips to secure itself properly the motherboard.

PCI-E connector:

It’s a connector that provides extra power for your discrete graphic card. This is required since the power via the PCIe x16 slots is limited to 75w. By providing extra power, graphic card manufacturers are able to provide higher performance. Some graphics use a 6-pin connector and use some use 8-pin. Some graphic cards require Dual PCIe connectors.

Just like the 4+4 ATX connector, PSU manufacturers have 6+2 PCIe connector so that you can detach the “+2 connector”, depending on the graphic card and the connectors it requires.

4-pin Molex:

 This is used by components such as DVD writers, older mechanical HDDs, certain 5.25” fan controller, PC- LED, Cathode tube and other internal add-ons.

Fun Fact: Molex is probably the oldest connector ever to be used for a PC. Originally it was made for certain electrical equipment and appliances, dating back to late 1960s. Even the early mechanical hard drives that were made available for consumers used Molex and continued until older 3.5” HDD. The connector form-factor for hard drives changes, and hence the SATA power connectors.

These don’t have clips, but the pins on the devices and accessories and the connector on the port is deep enough to keep it in place properly.

SATA power connector:

SATA power connectors are originally made for hard drives, but its naturally used for SSDs as well. These are lot thinner than Molex.

In some motherboards that require more power for multi-GPU based GPU setups, the motherboard has an additional connector to provide power for the PCIe slots. Most motherboards use a 4-pin Molex and some motherboards use a SATA power connector.

Just like Molex, SATA power connector does not have clips, but the connector on the SATA is deep enough to keep it in place properly.

Floppy power connector:

 It’s a smaller sized connector which was originally made to power up floppy disk drives, a very old and obsolete storage medium. However, there are certain types of devices which requires floppy connectors- like sound cards. An example is Asus Xonar DX, a discrete sound card that require additional power from the floppy connector.


  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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