PCIe cables are primarily used to provide power to installed graphics cards and other large expansion cards that require power. PCIe cables connect directly from the power supply to the installed PCIe expansion card; the Photographers card.
A typical PCIe x16 slot that you install the graphics card into provides 75 watts of power. This, however, is not nearly enough for many mid-to-high-end graphics cards.
In order to meet the power requirements of these large and demanding cards, PCIe cables are used. In the text below, we explore in detail what PCIe cables are used for, how they are connected and what their uses are.
While most expansion cards such as a network adapter, sound card, video capture card, etc., do not require PCIe cables – because they get enough power from the slot itself.
Graphics cards on the other hand, require additional power supplied directly from PSU.
Depending on the card you have installed, you may need one, up to three or more PCIe power cables.
What are the uses of PCIE cables?
So as mentioned earlier, PCIe cables are used to connect power-hungry devices like the graphics card to the power supply.
For most PCIe expansion cards, the power provided by the PCIe slot itself will suffice. However, for demanding cards such as graphics cards, the 75W provided by the PCIe x16 slot is not enough.
It should be noted here that only mid to high-end graphics cards need PCIe cables to supply additional power.
Some graphics cards do not require power cables
Many lower-end dedicated cards do not need to be connected to a PCIe cable.
Take the NVIDIA GT 710 for example. This is a very basic card that is primarily purchased to enable video output on systems as well as add multi-display capability.
This is far from being a gaming-based graphics card and therefore requires very low power.
As such, this graphics card does not require an external PCIe power cable. He can get enough power from the X16 slot he’s in.
Also Read: Do Graphics Cards Come With Cables?
Some require multiple 3 x 8 pin power cables
Compare this to the top-of-the-line ASUS ROG Strix NVIDIA Geforce RTX 3090 below.
This graphics card requires huge 3 x 8 pin power cables.
The bottom line is that when you buy a new PCIe device, especially a graphics card, it is important to check its power requirements and confirm if the PSU can supply it.
How to connect PCIE cables to the expansion card
We have already established that some PCIe devices may need more power, and this has to come directly from the power supply.
You can use a PCIe power cable for this by routing it from the PSU and plugging it into a PCIe card for it to work. Components that require this include high-performance graphics cards.
Route the power through the power supply unit
Power supplies come with PCIe power cables. However, the amount of PCIe cables you get depends on the PSU model.
The most recommended type of power supply for gamers and workstation systems are modular power supplies. These have additional connectors for mounting more PCIe power cables if needed.
Let’s look at an example. The following power supply unit comes with two 6 + 2 pin power cables built in and ready to use. So, I can connect to a graphics card that has a 2 x 8 pin power requirement.
In the following image, I connected the 6 + 2-pin power cables to a graphics card that has a 2 x 6-pin connector requirement:
Note that the additional +2 pin on both cables is now provided. It should be noted here that all power connectors on your graphics card need to be connected.
So, given the spare +2 pins, I could have connected a larger graphics card with a 2×8 pin requirement as well.
Now if I want to connect a larger power that has a connector requirement of more than 2 x 8 pins, I can use the power supply’s modular capacity.
You can see above that this power supply has additional power sockets due to its modular nature. Thus, I can connect more PCIe cables to this if needed.
Although, I will have to buy the extra power cables myself. So basically, your graphics card will determine whether or not you will need a PCIe power supply cable and how many.
The manufacturer will make this information available in the form of the number of power connectors the graphics card has.
Also, make sure that in addition to sufficient PCIe connectors, the PSU also has an adequate power rating. This is because some high-performance cards have high power requirements and overloading the PSU may result in a drop in performance.
So even if you can meet the power connector number requirements, you need the right size power supply.
PCIe power supply cables and basic types
There are many PCIe power cables that feature their own PIN configuration and power supply capability.
6-pin power cable
These are the smallest devices available and can deliver up to 75 watts of power.
8-pin power cable
This 8 Pin PCIe cable has a power delivery capacity of up to 150W. You may be wondering how a 6-pin generates 75 watts and an 8-pin doubles that capacity without doubling the pin count.
This relates to the fact that not all pins in a cable provide power. Some pins play a different role such as grounding, sensing/signaling, etc.
6 + 2-pin cable
We saw this in our example above. The 6 + 2 pin connector is basically an 8 pin cable that can provide lower and higher power depending on the connector requirements of the graphics card. Hence, here you get more flexibility.
12 pin cables
These are the latest connectors that NVIDIA has developed to meet the needs of the RTX 3000 series graphics cards
Depending on the cable gauge, a 12-pin cable can supply 500-600 watts of power.
These are fairly rare at the moment and are only found on very high-end systems.
PCIe pigtail cables
There are also PCIe cables with pigtail connectors. These basically have one end connected to the power supply and then split into two connectors on the other side.
So the cable above is an 8-pin braid cable. One end of it will go to the power supply unit. The other end has two separate 8-pin connectors that can be used on the graphics card.
There is a general debate about whether you should use pigtail cables or separate cables. Many hardcore enthusiasts think separate cables should be the way to go. However, others have demonstrated that pigtail cables do not result in a significant drop in performance.
PCIE cables and graphics card maximum power consumption
Depending on the type and amount of connectors on your GPU, the maximum power consumption can be summarized as follows:
You should now have a clear idea of what PCIe cables are used and how to connect them. Essentially, you provide power to your graphics card from the PSU.
Not all expansion cards that plug into PCIe slots require a PCIe power cable.
Understanding your power supply specifications, the cables available to you and the connector requirements on your graphics card are key to good power management for your system.