Essentially, you need to have as many PCIe cables as your graphics card needs. Depending on your GPU, this could mean a single 6 pin cable all the way to 3 x 8 pin cables on powerful cards like the NVIDIA RTX 3090.
Basically, PCIe components need to be powered, just like any other component on the motherboard. Usually, for smaller and weaker cards their power comes from the PCIe slot itself. However, some components, particularly the graphics cards, need a lot more power than your average add-in cards like network adapter, SATA expansion or video capture cards etc.
As such it is wise to measure how many PCIe cables do I need before you go about purchasing the right power supply unit for yourself. PCIe power cables do not come packaged with graphics cards. Instead, they come packaged with power supply units.
Often you will hear complaints regarding graphics card not working or not even initializing. This is often a power related issue.
You also often hear people ask if all the pins on the graphics cards need to be connected. The answer to this question is a resounding YES! You do need to have all the pins connected in order for the graphics card to work.
If your graphics card has 2 x 8 PIN requirements. Then, well, you need to provide it with 2 x 8 Pin PCIe Cables coming in from the Power Supply Unit.
Let us explore this topic a bit further below.
How Many PCIe Cables Do I Need?
The actual number of PCIe cables you need primarily depends upon the type and amount of graphics cards you have installed.
For instance there are some graphics cards like the NVIDIA GT 710 that do not require a PCIe cable at all. This weak graphics card receives its power supply from the PCIe slot itself.
Starting from mid to high and extreme range, you may find cards that need as low as a single 6 pin PCIe cable all the way to 3 x 8 pin cables on the likes of NVIDIA RTX 3090.
If you have two of NVIDIA RTX NVIDIA 3090 installed, then you will need 6 x 8 pin cables.
The rest of the common expansion cards like a video capture card, network adapter, sound card, USB hub, etc do not require a PCIe cable.
Visual Guide for PCIe Cables and Connectors
The graphics card above has a requirement for 2 x 6 pins.
However when inspecting my power supply, I see that it has has 2 x 6+2 PCIe Cable connectors:
A 6+2 Pin PCIe cable, has a single large 6 pin connector as well as an additional 2 pin split in case if you need more power. Basically, a single 6+2 pin cable can power an 8 pin slot on a graphics card.
However, the graphics card I have does not have a dedicated slot for an 8 pin cable. Instead it requires two separate 6 pin PCIe cables. Hence the additional 2 pins will be useless in this case and will not be utilized.
Here you can see that both PCIe cables available to me from the power supply are connected to the graphics card. However, both cables have 2 pins not utilized.
You have to have all the pin ON THE GRAPHICS CARD plugged.
What Uses PCIe Cables?
As mentioned, the most important expansion card that uses PCIe power cables is the graphics card because many mid to high range graphics cards draw far more power than the 75W provided by the PCIe X16 slot itself.
PCIe Power Cables and Connector Types
There are different types of PCIe power cable connectors and differ from each other in terms of how much power they can supply to the card.
The amount of PCIe cables and the type of connector you need would depend entirely upon the graphics card you install.
With the graphics card, knowing how many PCIe cables do I need is pretty straightforward. You will need to look at the Power Inputs Connectors either physically or through the specsheet of the card for this.
ASUS ROG Strix RTX3090 Spec Sheet as shown above tells you how many power connectors, aka PCIe cables, you will need. In this you will need three 8 pin PCIe cables.
The 6-Pin connector can provide upto 75 watts of power.
This is the most common connector used by many low to mid-range cards. So if your graphics card has power requirements of anywhere greater than 75 watts to 150 Watts max, you will likely need one 6 pin PCIe cable.
For a graphics that consumes 150 watts of power, 75 watts will come from the PCIe x16 slot and another 75 watts from the 6-pin cable.
The 8-Pin connector is typically found on cards that have a high power requirement. It is capable of supplying up to 150W from the 12V rail on the PSU to the graphics card.
With 8 pins, you get the chance to run more intensive cards that draw a lot more power from the system.
The 8-pin cable comes in two flavors. You can get one that has a single 8-pin connector in one terminal. The other comes as a 6-pin module with an extra 2-pin attachment. This one is more modular and can be used on both 8-pin and 6-pin cards (as seen in the guide above).
This is used by some of the newer cards like the lineup from NVIDIA’s RTX 3000 series. These may need an adapter since many PSUs don’t have the required 12-pin output connector.
Each cable with 12 pin connector can provide from 500-600 watts of power depending upon the wire gauge of the cable.
Pigtail PCIe Cables
For instance, the cable above is an 8 pin pig tail cable. It connects its one end to an 8-pin output connector on the power supply unit and then it separates into 2 x 8 pin connects on the other side.
With this you cable can either power a single graphics card that has a 2 x 8 pin connector or two graphics cards with single 8 pin connector.
There many gamers and enthusiast who debate whether separate cables should be used instead of pigtail cables for powering graphics cards.
Many hardcore enthusiast believe that separate cables should be the way to go. However, others have proven, as shown in the analysis below, that pigtail cables have a minimal impact on the performance.
Cables and Graphics Card Maximum Power Consumption
The following table highlights the number and type of PCIe cables used and the corresponding max power consumption by the connected graphics card.
|6 Pin Cable|
|8 Pin Cable|
|12 Pin Cable|
|75W||1 x 75W||0||0||150W|
|75W||0||1 x 150W||0||225W|
|75W||2 x 75W||0||0||225W|
|75W||1 x 75W||1 x 150W||0||300W|
|75W||0||2 x 150W||0||375W|
|75W||1 x 75||2 x 150W||0||450W|
|75W||0||3 x 150W||0||525W|
|75W||0||0||1 x 600W||675W|
More Than One Power Connector on GPU
On most mid-high end cards, you can expect to find more than one power connector.
Sometimes cards have non-uniform pin configuration as well. For example, NVIDIA’s GeForce GTX 1080Ti graphics cards come with two connectors. An 8-pin connector and a 6-pin connector.
You can’t use a single PCIe cable for both connectors. In this case, you will need two PCIe cables to power the graphics card. And, because it has high power needs, about 250 Watts, the 300W supplied to it will be sufficient.i.e 75 from PCIe x16 slot, 75 from 6 pin connector, 150 from 8 pin connector.
Also Read: How to Check How Many PCIe Lanes Do I Have?
Adding More PCIe Cable and PCIe Cable Adapters
If you have a modular Power Supply Unit, you can add more cables to the PSU. You can also use the pigtail cables mentioned above which splits a single cable into multiple connectors.
Also, some PSUs do not have the required type of power connectors. To get around this, you can use an adapter like the one you see above.
If you use an old PSU, you can increase the PCIe power cable by using a Molex adapter.
It is pertinent that you do not exceed the your Power Supply Unit’s output power rating when installing PCIe cable adapters.
I advise that you use the following automatic calculators to gauge if your PSU is sufficient for your build:
Also Read: What are Motherboard Standoffs?
To know exactly how many PCIe cables do I need, users need to understand their cards and power supply units.
Depending on the card, you can have different power connectors which may require you to have different type and number of PCIe cables. Again. you do need to have ALL the connectors GPU connected to the power supply.
Furthermore, you may end up needing an adapter to convert the available power connectors to the more standard 6 and 8-pin ones, or even the 12-pin one.
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