PC power supply connections explained: definition & pin assignment

The connectors on your PC power supply and all the cable connections are the most intimidating aspects of building a gaming PC for many. At first glance, the pin assignment of all your power supply cables PC seems overwhelming, and you don’t even know where to start. But it’s all half as wild.

With our step by step guide, you will recognize all power supply cables, understand their function, and then assign them correctly. Connecting the cables to your PC power supply is surprisingly easy afterwards. Just follow our guide here at your own pace, and you’ll be fine (you’ll even learn some cable management). Let’s get started right away!


PC power supply connections: overview for a modular model

To show you what the connections look like on a modern, fully modular PC power supply, look at the picture below.

If you can call a modular (or semi-modular) power supply your own, then you are doing something good for yourself and your PC. Because these have removable cables with which you can conveniently only connect the cables to the power supply you need for your individual hardware.

Accordingly, it would help if you only connected the necessary power cables to the power supply (you will find out which ones are in a moment). It is up to you whether you attach the cables before inserting the power supply unit into the case. This is a bit complicated with some cases.

PC power supply connections

As you can see, the pin assignment on a newer PC power supply is self-explanatory, as everything is already labelled. You should always find a label on any reasonably good power supply, so you shouldn’t have any problems attaching the cables.

If you’re not sure which cables to use for your PC components, don’t worry. Just go through our article and gradually connect the cables you need.

With every PC, you have to connect the 24-pin motherboard power cable and the 8-pin CPU power cable without exception. Keep unused cables in a safe place for possible future use.


Power supply cables PC: Brief overview

In the following, we give you a brief overview of the most important cables and their function. So that you know which ones you will definitely need. Below we will explain to you specifically how you plug all cables and where.

Some main cables must always be connected to the PC power supply connections, but some are optional:

  • 24-pin power supply for the mainboard (always required)
  • 4/8-pin EPS12V power supply for the CPU (always required)
  • The power cord to power the system (always required)
  • 6/8 pin power supply for the graphics card (usually required)
  • SATA power supply for storage devices (usually required)
  • MOLEX power supply for accessories (optional and partly outdated)

You can find out what the cables look like in the individual steps below – there the pin assignment for each individual cable is explained in detail.


Power Supply cables guide

One thing first: You can find more tips on cable management in the last step of this article. Before you connect your power supply cables to your connections and components, you should familiarize yourself with some of the basics because this allows you to try to do a little cable management right at the beginning or at least to prepare it. Otherwise, it could be that you have to unplug all the cables again at the end and do double the work.

If you connect every power supply cable to the motherboard and other components, then lead all power supply cables through the eyelets and cable holes provided for them where it makes sense. The number and position of these cable routing holes are different for each housing, so there is no magic formula.

PC power supply connections

The aim is to make full use of the space between the motherboard compartment and the back of your case. Since you can hide a large part of your cables here in most modern housings, the front is much tidier, and you have more space to work.

When laying cables in this rear area of ​​the housing, make sure that you can later easily open and close the housing’s sidewall (without damaging your cables).

In addition to using the back of the case to hide cables (almost behind the mainboard), some cases also have other areas for this. To hide excess cables, the cover on the case’s underside is often a good choice, where the power supply is installed (if your case has one). Or you use an unused drive bay on the front.


Power supply connectors on motherboard

Before you connect the power supply cables of your power supply unit, a short important note, you should also know where to connect the power supply cables to the motherboard.

Plugging in power supply cables can sometimes require some pressure. This ensures that the cables are properly connected (to avoid an unstable system due to loose power connections). You may even have to apply a lot of pressure to plug in the 24-pin mainboard power connector.

Before connecting a power supply cable, make sure it’s the right way round (there is only one right way) by matching the pin patterns on the underside of the power supply connection with the pin patterns on the motherboard (or other components). In no case should a power cord be pushed too tightly into a port the wrong way round? You risk bending or breaking the pins.

This is what the power supply connections PC look like

Each power supply installation requires two direct connections to your motherboard—one for the mainboard’s main power supply and one for your CPU. The connections to which you connect them to a mainboard are generally in the same place. You can see where the two largest PC power supply cables are connected to your mainboard in the following picture.

PC power supply connections

The 8-pin CPU cable (orange) and 24-pin mainboard cable (red) are connected here

There is only ever one place for the 24-pin connector. In this example, however, you have 8-pin connectors, of which you actually only need one. A second one can only be found on expensive motherboards, and this is only needed for extreme overclocking (if at all).

What to do if a power supply cable is not long enough or is missing?

You may encounter two problems during the following steps to connect the power adapter cables:

  • a particular power cord is not long enough to connect correctly (maybe you are building it in a large enclosure)
  • Your power supply lacks a certain connection that you need

In both cases, you can easily solve the problem with an extension and/or an adapter. Just look for suitable solutions online. However, something like this rarely occurs with modern power supplies.


Connect the 24-pin PC power supply cable to the mainboard

Now we can finally start wiring your PC. The main task of the power supply unit PSU is to supply your mainboard with power. This is done via the 20-pin or 24-pin connector.

Therefore, we start with the large 24-pin main connector for the mainboard power (also called the ATX connector). With modern power supplies, this is either a straight 24-pin plug or a 20 + 4-pin plug. This is often also marked with the word “MB” on the cable.

Some motherboards only require a 20-pin motherboard power connector. In this case, you only plug in the 20 pins (the other 4 pins stay on the side). However, all current mainboards require a 24-pin power connection.

24-pin PC power supply cable

The figure above from the previous paragraph shows what the 24-pin connector on a mainboard looks like. This is exactly where you have to connect your power supply cable. In many cases, this port is labelled with things like “ATX_PWR1”, so you shouldn’t have any problems finding it.

Align the pins correctly and insert the 24- or 20 pin connector + 4-pin connector carefully, but with a little pressure. You may have to use a little more force so that everything is properly seated (and so that the plug cannot loosen). It is best to hold the connector by the edge with your thumb and index finger to align it correctly. To do this, place the motherboard on the cardboard box provided and hold it in place while you push the connector in.


Connect the 8-pin CPU power cable to the motherboard

The 8-pin power supply cable for the processor (also called P4 or EPS connector) must also be connected to the mainboard. This gives your CPU the juice it needs nowadays.

8-pin CPU power cable

This is what the CPU power cables look like from your power supply

Look for a 4 + 4-pin connection on the motherboard, which should be near the CPU socket (usually in the top left corner). Often you will see writing like “CPU_PWR1” or something similar on the surface of the mainboard. It is best to read briefly in your mainboard manual again if you are not sure.

Most modern motherboards require you to plug in all 8 pins, but some may only require 4. In this case, you can connect one of the two 4-pin headers.

Again, carefully align the pins (the connectors only fit in one direction), hold the motherboard by the side for better control, and push the cable firmly and flush into the connector.

As you can see in the picture above, modern PC power supply cables are marked accordingly with “CPU.” You can’t go wrong with that anymore.


Connect the PCI express connector graphics card

Most modern graphics cards these days require a direct power connection via the power supply. However, some older, lower power consumption GPUs (such as the GTX 1050 Ti) do not need a dedicated power supply and receive all of the power they need directly from the motherboard’s PCIe slot through PCI express connector.

If your graphics card needs a direct power connection (this is stated in the technical data, or you will find pin connections like the ones shown below), it is either a 6 or 8 pin connection or a double one in the respective version (for more power-hungry GPUs). For example, an RTX 2080 Ti, like the one shown below from MSI, requires two 8-pin power connectors.

Connect the PCIe cable to the graphics card

Every decent modern power supply comes with (at least) two PCIe power connection cables. Since these come in the form of 6 + 2-pin connections, you can either connect all 8 or only 6 pins to the graphics card. It would help if you connected all PCIe power cables that you need for your particular graphics card. The same applies here: If you are unsure how much power your GPU needs, read the manual.

In the rare event that your power supply does not have enough PCIe power cables for your graphics card, you can use a Molex-to-PCIe adapter (molex cable power supply). These are included with some graphics cards, but you should only do this as a last resort, as this is far from ideal. It is best to use the cables shown here:

 PCIe cables

As you can see, the PCIe cables of newer power supplies are always marked with “VGA.” This means that you always know which cables to connect to your graphics card.


Connect Power Supply SATA cable to Hard Drives and accessories

Next, you have to connect your SATA power cable to the power supply. The SATA connection has made the Molex superfluous.

Not to be confused with the SATA data transfer cables that should come with your motherboard (and which you connect from the motherboard to the hard drive). 

These SATA power cable adapter supply power to your hard drives (SATA SSDs or HDDs), optical drives, and other accessories such as AiO water coolers with power.

cables

Connect the power supply SATA cable from your power supply unit to all hard drives, SSDs, or optical drives. Due to the L-shape, you can only insert them in one direction. Often you have several connectors hanging on a cable harness, which means that you can supply several devices with power with one cable.

If you have many SATA drives or accessories and your power supply doesn’t have enough SATA power cables to connect them all, you can use the PSU Molex cable on your power supply with a Molex-to-SATA adapter.

sata power cable
Molex-to-SATA adapter
ssd
M.2 SSDs do not need power cables (or data cables). These super-thin SSDs are plugged directly into the motherboard and draw their power exclusively from it.

Connect 4-pin Molex Cable (optional)

SATA connectors have almost completely replaced Molex connectors. However, some power supplies still have these, and you may still need to use them for accessories such as some CPU water coolers or case fans. These are the 4-pin connectors that look like this (and may be labelled as “peripheral cables” and “PATA” in the power supply specifications or directly on the power supply connections):

4-pin Molex power cables

The molex cable power supply are often used when you cannot connect your case fans directly to the mainboard because there are too few fan headers.

Ideally, however, you want to connect case fans to the fan headers on the motherboard. Because if you connect the case fans directly to your power supply, they always run at 100% performance (you cannot control them).

If you don’t need Molex connectors and are using a modular power supply, save the cables. Otherwise, you have to stow it somewhere in the case.

Sometimes you really need a lot of strength here to connect them properly. So don’t be afraid to be a little rough with these guys. Even when you pull them off, these things tend to get stuck.


Cable management tips

As already mentioned, with the pin assignment of your PC power supply connections, all cables should run through the rubber holes in your housing so that everything is neatly tidy. As soon as you have connected all the cables, it would help if you heeded the following tips.

Why cable management?

The whole thing makes sense, even if you don’t have transparent housing. Because cable management is not just about aesthetics, you can also achieve other advantages:

  • It is easier to work in the housing
  • The life of your PC is extended by maximizing airflow and avoiding dust
  • Loose cables are avoided, which avoids possible damage to other components

How extensively you should clean up your mess of cables depends on your build and is ultimately a matter of taste. While a messy build isn’t the end of the world, we recommend investing the time. It’s worth it in the long run!

pc cables
Bad cable management – please NOT like that!

Cable management for non-modular PSU

If you have a modular PSU, cable management is much easier – you have to deal with fewer cables.

With a non-modular PSU (power supply), you must first run the entire cable harness through the case’s back. Then you connect all required single cables to the connections and try to store the unnecessary ones somewhere in the housing. It is best to lay the unnecessary cables under the hard drive cage, the power supply cover, or tie them to eyelets with cable ties.

Avoids tangled cables

It would help if you also used zip ties to bundle groups of cables and position them on the sidewall. Avoid that cables overlap, knot, or otherwise get in the way. Some cases offer you practical Velcro fasteners or special eyelets for cable ties on the back of the mainboard partition, making things easier for you.

Think about the airflow

When routing the cables, think about the airflow and try not to obstruct your cooler or case fan with cables if possible. If your case doesn’t offer many cable management options, don’t worry too much – do your best.

Don’t forget the power cord and switch

So we come to the end of our little guide on pc power supply connections. Logically, you still have to connect your power plug to the back of your power supply and set the power switch to “On” and start your PC.


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