When it comes to choosing and installing a GPU, a lot of things need to be considered besides just the computational capacity of the card and the amount of memory you’ll have at your disposal. One of the most important consideration is how many PCIe lanes does a GPU use?.
Generally, a GPU uses 16 PCIe lanes. However, once you start delving into multi-GPU configuration then things start to change. With an SLI or Crossfire, the GPU can use 8 or even 4 lanes, respectively, to operate.
While most of the time, users want the best for their system, it is important to know the specifications of your device so that you end up purchasing the correct module for your board.
Knowing how many lanes are needed by a GPU will save you some problems down the road. Compatibility issues may not arise, but it would be better to know that your motherboard has enough PCIe lanes to fully utilize the GPU you spent good money on.
So How Many PCIe Lanes Does a GPU Use?
As mentioned earlier, a GPU can use 16, 8, or 4 lanes depending upon the brand, number of available PCIe lanes, and the amount of GPUs installed.
To discuss, let us breakdown this question into parts.
What is PCIe Lane?
Modern motherboards come with one or several PCIe slots depending mostly on the size and the model of the board.
PCIe (Peripheral Component Interconnect Express) is a standard that is used to connect high-speed devices to your motherboard. This lets you add more components and essentially improve your setup over time.
PCIe devices need to communicate with other components on the board, preferably the CPU, and this is where PCIe lanes come in.
PCIe lanes are made up of two pairs of connections where one sends data from the device and the other receives data from other devices.
PCIe slots come in different sizes and fixed lane counts so that you have either 1, 4, 8 or 16 lanes depending on the type of PCIe slot. A 32 lane PCIe slot also exists in the specification but it is rare.
PCIe Slot Size Does NOT Correspond to Lanes!
This is a very important point to take not off.
Many confuse the PCIe slot size with the amount of lanes it has. That is hardly the case.
For instance, sometimes you can find a PCIe X16 sized slot offering only 8 lanes. Sometimes it can even offer a mere 4 lanes despite having the large size.
The GPU, What is It?
Just like many users are familiar with a CPU, a GPU is also an important component to be familiar with. A GPU (short for Graphics Processing Unit) is an electronic circuit that specializes in one thing, graphical computations.
These are great for both professional and novice gamers alike as they are more efficient at rendering than a regular CPU.
Even though the word “graphics” is part of the name, these microprocessors are used for more than just graphics rendering. They’ve been widely used in business applications such as Bitcoin mining and training AI models due to their fast computation speeds.
GPUs are a common staple for people building hardcore rigs that can handle anything thrown at them including graphically demanding applications. For this reason, you would want a board that has enough PCIe lanes to handle all the bandwidth that the GPU puts out.
How Many Lanes on a Graphics Card?
Most Modern GPUs plug into an 16X PCIe slot. This is because a most modern GPUs have 16 PCIe lanes to occupy.
Of course, the number of lanes that a GPU needs to run optimally will depend highly on the number of graphics cards you will install.
The GPU itself sits inside a graphics card where it has the necessary circuitry to interface with the PCIe slot on your motherboard.
As mentioned, data on these slots is transmitted through lanes to the CPU. Hence, with enough lanes, you can use your GPU to its fullest potential as long as the CPU you pair it with has the necessary capabilities to support all the lanes.
However, when running a single GPU, the device will require 16 lanes to function optimally.
16X PCIe Slot – 16 Lanes
With this slot, you get a total of 16 lanes. This is the current highest lane count you can get on many consumer-grade motherboards and it also has the highest bandwidth.
If you only have a single graphics card, this is the slot you will use.
Since it provides the highest bandwidth, you can expect to get the best performance from your graphics card when you use a 16X slot.
The first generation PCIe standard gives you about 4.0 GB/s of throughput and as you move to the second, third and fourth generation, the speed theoretically doubles. This gives you a whopping 31.5GB/s of throughput on the X16 slot of PCIe 4.0.
16X PCIe Slot – 8 Lanes
This slot looks similar in size to the X16 slot on many boards, however, it has half the lanes of the latter and half the bandwidth.
Nevertheless, this slot will run a graphics card too.
An X16 graphics card on an X8 slot will operate at the X8 slot’s bandwidth. For this reason, you may end up underutilizing the GPU.
Situations Where GPU Uses 8 Lanes
Users are often encouraged to plug their GPU into a slot that can accommodate 16 lanes. You may sometimes end up using 8 or less lanes when running multiple GPUs in one motherboard.
This can be done in either SLI (NVIDIA GPUs) or Crossfire (AMD GPUs) and it allows you to split your graphics processing load across multiple graphics cards.
When you have a single GPU and you put it into a 16-lane slot, as long as your CPU can handle the lanes and all the 16 lanes are available, you will use this single GPU with the 16 lanes.
However, if you have only 16 available lanes and you plug in two GPUs into two X16 lanes, the device will utilize each of the GPUs but each will only work with 8 lanes.
This is a problem faced when your CPU doesn’t have enough lanes for both GPUs.
To beat this, however, you can get a processor with a high PCIe lane count so that you don’t sacrifice some of your GPU’s lanes. However, high lane-count CPUs are quite expensive.
Also Read: Best Motherboards for SLI
16X PCIe Slot – 4 Lanes
This slot also looks like a full 16X sized slot but only offers 4 lanes.
This slot can also occupy GPU but ONLY FOR AMD CROSSFIRE.
You see, AMD graphics cards can operate on 4 lanes. NVIDIA graphics cards cannot.
In other words, in order top operate AMD crossfire, you can have one graphics card installed in the X16 – 16 lanes slot and the other in the the X16 – 4 lanes slot, and they both will work.
With GPUs, you always want to ensure that you’re getting the maximum power you can from the card because they are expensive.
GPUs can interface with your motherboard using the PCIe slot and hence provide you with better graphics processing capabilities.
However, not all PCIe slots are the same so you will need one that can fit your GPU best. So how many PCIe lanes does a GPU use? Simply put, modern GPUs work optimally with 16 lanes. A 16 lane card will, need to be plugged into a 16 lane PCIe slot to work effectively.
However, if you want to installed multiple GPUs and since a typical processor only has 16 lanes to offer, it divides the lanes between the multiple cards.