What is a Modular Power Supply Unit?

What is an ATX modular power supply unit? What is the difference between a fully modular vs semi modular PSU? Find out the answers here.

A modular unit is a computer power supply where some (or all) of its power cables and connectors can be detached and removed. This differs from a regular power supply where all its power cables are permanently hard-wired and non-removable.

While ATX modular power supplies have been popular among computer enthusiasts for a good number of years (since 2006 and earlier), they have just found their way to the mainstream market in recent years... thanks to falling prices and increasing consumer awareness.

See the image below for an example of modular PSU. Take note of its sockets (that allow you to plug in and detach power cables):

Modular Power Supply

Fully Modular vs Semi Modular Power Supply Units

There are in fact two types of ATX modular power supplies: Fully modular and semi modular.

Fully modular indicates that every power connector is detachable and removable. High end power supplies tend to have a full modular design. It's no surprise given that they appeal to hardware enthusiasts and cable management zealots by allowing for total cable customization, such as changing the length, color and even sleeving of the modular power connectors.

Semi modular units have a few power cables that are permanently fused to the power supply while the remaining ones can be detached. The image below shows a semi modular power supply unit with its full set of detachable power cables:

Semi Modular Power Supply

From the image above we can see that the essential cables are often hard-wired, such as the ATX power connector (that powers the motherboard) and the P4 power connector (that powers the CPU).

Detachable power cables make up the rest: SATA connectors (for hard drives and optical drives), Molex connectors (for older drives and case fans) and PCI-E connectors (for discrete graphics cards). For more details, check out our picture guide to the different types of computer power connectors.

In general, we recommend semi modular over full modular power supplies. Semi modular models cost slightly less (cheaper to manufacture) and tend to have higher power efficiencies (hard-wired connectors = lower electrical resistance).

For most consumers, there is only one practical reason to go for a fully modular PSU: If you have a very small and cramped computer case. In this situation, a power supply that is fully modular allows you to swap out your standard length (~60 cm) motherboard and CPU power connectors for shorter ones (~35 cm).

Are Modular Power Supply Cables Interchangeable?

Modular power cables are NOT interchangeable across different brands and manufacturers in general (e.g. you cannot pair Seasonic power connectors with Corsair power supplies).

It's a real shame but there is no universal standard for modular power connectors. Different PSU manufacturers produce in-house connectors that only work with their own power supply units. The image below shows the variation in modular power connectors between two different brands:

Even power supplies from the same brand could be using different types of connectors. Whenever possible, you should stick to modular PSU cables made for your particular brand and model.

If you're buying modular cables of the same brand but different models (e.g. Seasonic G Series vs Seasonic X Series), you should check with the manufacturer first. Since most manufacturers do not state whether their modular power connectors are interchangeable for different models (though they really should), you'll have to email or call their customer support.

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