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A Graphics Card running at x8 instead of x16 is one of the most annoying problems that a graphics card user can encounter. Just to tell you, I have also faced this problem and it was really frustrating to detect the cause because it takes into account all the factors related to the motherboard, operating system, and the graphics card. Sometimes, it may not be a problem at all and simply a misunderstanding, because, at low GPU loads, the PCIe bus runs at lower speeds to conserve power, which is also a part of the power management features in windows, and at higher GPU loads, it switches to higher PCIe mode to deliver the maximum performance needed by the games or applications
Normally, at low loads, the PCIe x16 bus runs at PCIe x16 1.1 and as the load increases, it goes to a high bandwidth state which is generally PCIe x16 3.0, assuming that your graphics, CPU, and motherboard supports PCIe 3.0 standard. So, if the PCIe x16 bus switches from PCIe x16 1.1 state to PCIe x16 3.0 as the load increases, then you don’t have to worry about it at all, because everything is working properly as expected. The point of concern is when your graphics card is capable of running at PCIe x16 3.0 but is running at PCIe x8 1.1 or PCIe x8 3.0, even at full GPU load. For example, in the image below, you can clearly see that the graphics card is only utilizing x8 lanes and is not working at its full capacity, which is at x16, even though the PCIe standard is switching from PCIe 1.1 to PCIe 3.0.
There can be several reasons that can lead to this problem, and in some cases, there is no definite answer to it. Sometimes, the issue is related to hardware and sometimes it may be due to firmware and software, but in most cases, the issue lies with the hardware only. If you are lucky, then you can resolve this issue in minutes but if you are not then it can take a lot of effort and time to figure out the exact cause of this problem. In some cases, you may have to live with this problem, because it cannot be fixed due to the faulty hardware. So, here I am going to list down the various factors that can contribute to this problem, along with their solutions or fixes.
How to Check and Verify GPU PCIe Speed?
The best and the easiest way to check that your graphics card is operating at full PCI Express speed and is using all the 16x lanes is by using the GPU-Z, which is the best graphics card information utility. It has a built-in rendering test that pushes the GPU load to 100% and lets you check whether the Graphics Card or PCIe interface is operating at its maximum potential or not. To test this, download the GPU-Z utility and run it. Now, in the Bus Interface section you will see the maximum PCIe bus interface supported by the graphics card, and along its side, the one that it is currently working on. Below, you can see that the graphics card supports PCIe x16 3.0 but is working on PCIe x8 1.1 to save power when the GPU is idle or the GPU load is minimum. Now, click on the question mark next to it. A new window will open along the side, on which there is the Start Render Test button. Click on the Start Render Test button and this will start a GPU render test that will put your GPU usage to 99% or 100%.
Now, if the PCIe Bus Interface changes from PCIe x8 1.1 to PCIe x16 3.0, then it means your PCIe bus interface is operating at full bandwidth and speed. However, if it changes to PCIe x8 3.0 or remains at PCIe x16 1.1 only, then it is an issue and you have to find the cause of it.
Note: In the above scenarios, both the graphics card and motherboard support the PCIe 3.0 x16 interface.
How much performance loss can be there?
If your PCIe x16 bus is working at PCIe x8 at full GPU load, instead of x16 (both PCIe 3.0), then you normally don’t have to worry about the performance as such. This is because even if you have a high-end graphics card like GTX 1080 Ti then also it will be nearly impossible for it to saturate the PCIe 3.0 x8 bus when it is running at its maximum performance or capacity. However, you may encounter a tiny performance loss in some applications or games, which is around 1% to 2% at max. However, you can suffer significant performance loss then the graphics card runs at PCIe 1.1 x8, PCIe 2.0 x8, or at PCIe 3.0 x4, given that both the graphics card and motherboard are PCIe 3.0 x16 capable.
Why is GPU / PCIe running at x8 instead of x16?
Here are the various causes (with their solutions) that can make your graphics card run at x8 instead of x16 in your PCIe x16 slot.
GPU is not in the top PCI-E x16 slot
The first thing to do is to check whether you have the graphics card is installed in the first PCI-E x16 slot, because if you have two or more than one PCIs x16 slot then in most of the motherboards, the first PCIe x16 slot runs at maximum PCIe bandwidth, which is x16, while the second PCI-E x16 slot runs at x8 speed only.
Check if CPU, GPU & Motherboard supports PCIe x16
You also have to make sure that your CPU, Motherboard, and GPU support PCIe x16, whether it is a PCIe 3.0 or PCIe 2.0 standard. You can check this information on the manufacturer’s website of the CPU, motherboard, and graphics card. If your CPU does not have PCIe 16 lanes then your GPU won’t run on PCIe x16 speed, even if the motherboard supports it. On the other hand, if the CPU supports PCIe x16 lanes for the graphics card, but your motherboard or graphics card is limited to only PCIe x8, then your graphics card will run at PCIe x8 only.
Reseat the graphics card
One of the most important things to do, when you face this problem is to reseat your graphics card. Remove the graphics card from the PCI-E x16 slot, clean the PCI-E connector contacts with isopropyl alcohol, and put it back in the PCI-E x16 slot properly. This is because, sometimes dust or even some part of the warranty sticker can be present on the PCI-E connector, which can result in this issue. Also, make sure that the motherboard PCI-E x16 slot is clean and that there is no dust present in it. You can clean off the dust using an electric air duster by blowing air on the PCIe x16 slot.
Multi-GPU Setup [SLI or CrossFire]
If you have two graphics cards installed in SLI or CrossFire multi-GPU mode, then the graphics cards will run at PCIe x8 only, because the CPU PCIe x16 lanes get shared between the two cards equally, even if the first PCI-Express slot supports 16 PCIe lanes.
PCI-E Lanes shared with other Components
[NVMe SSD or PCI-E x16 Expansion cards]
If you have PCIe NVMe SSD installed in your computer, then it might be possible that the NVMe SSD is consuming some of the PCIe lanes of the CPU, and this will result in your graphics card running at lower PCIe x8 speed. This can happen with some motherboards where the chipset PCIe lanes are not configured to be utilized for NVMe SSDs. So, here you can remove the NVMe SSD from the M.2 slot to check whether your graphics card is now operating at full PCIe x16 speed or not. This issue can also happen if you have a PCIe expansion card (sound card etc.) in the adjacent PCIe slot, which is eating up your PCI Express lanes and making your graphics card run at PCIe x8. So, here also, you can remove the PCIe expansion card and can check whether the PCIe status of the graphics card reverts to the PCIe x16 or not.
PCI-E power cable plugged in graphics card
If your graphics card requires external PCIe power connectors (6-pin/8-pin) then make sure that they are plugged in properly and also that the connectors are working fine. In most cases, if the 6-pin / 8-pin PCIe connector is not connected or is faulty then your computer won’t boot, but in some cases, the graphics card may work but will operate at much lower speeds. So, keep this little thing in mind and check your Power Supply PCI-Express power connector also, when your graphics card is operating at PCIe x8 instead of PCIe x16.
Disable USB 3.0 Turbo in BIOS
If you have a motherboard that has Turbo USB 3.0 or USB 3.0 Turbo option in the BIOS then disable it, because Turbo USB 3.0 feature consumes your CPU PCIe lanes at the expense of some extra boost in USB 3.0 speed, and makes your graphics card run at PCIe x8 speed only. You can find this ‘Turbo USB 3.0’ feature implemented in many of the Gigabyte Motherboards. You can find this option in the BIOS, under the Integrated Peripheral section, and here you can disable it safely.
Update Motherboard BIOS
If your motherboard BIOS is outdated and a new update is available from the motherboard manufacturer, then you can update your motherboard BIOS to see if the problem is not related to the BIOS. Also, updating your motherboard BIOS is a good thing because it can have security fixes, bug fixes, new features, and support for newer hardware. Updating the motherboard BIOS is very easy and you can do it by using a USB Flash drive. You can download the latest BIOS for your motherboard from the manufacturer’s website and can consult the manual for instructions on how to flash or update it.
Update Graphics Card BIOS
You may also try updating the GPU BIOS, but do this only when you have the right copy of the updated BIOS of your graphics card, and you have tried all the other things. This is a risky thing to do because a slight error on your side can brick your graphics card for life. Generally, I do not advise updating the GPU BIOS, and it should only be done when you have some serious issues with your graphics card and this is only the last resort when you have tried everything else.
Windows PCI-E link state power management
Make sure that your PCI Express Link State Power Management setting is not set to Maximum power settings. You can check this by going to Control Panel->Power Options->Change plan settings (for the selected plan)-> Change advanced power settings->Expand PCI Express option->Link State Power Management->Setting. Here, select Off or Moderate power setting, if the Maximum power savings option is selected earlier.
Reseat CPU and Clean Pins / Contacts
You can also check whether your CPU / Motherboard pins are clean and there is nothing obstructing them. This is because I have seen in some cases where if one of the pins is dirty and not making contact with the CPU and motherboard, then all the CPU PCIe lanes may not be available for the graphics card, and this can cause your GPU to run at lower PCIe x8 speed instead of x16.
Install Chipset & Video drivers
Clean install the video drivers by removing the older ones using Display Driver Uninstaller (DDU) utility to check whether the issue is from the driver side or not. You can also install the latest chipset drivers for your motherboard to confirm that it is not a driver-related issue.
A faulty motherboard can also be a cause of this issue and you cannot do anything in this case. The only thing you can do here is to replace the motherboard. To check whether the culprit is the motherboard, you can try running your graphics card in another PC (friend’s PC or other), and if the card runs at full PCIe x16 speed in that system, then the issue is with the motherboard only, given that you have already tried all the above-mentioned solutions. If the motherboard is under warranty, then you can ask for a replacement from the seller.
Faulty Graphics card
Like a faulty motherboard, the graphics card can also be faulty. This you can check by running your graphics card in another system that supports PCIe x16, and if the card still runs at PCIe x8, then most likely the issue is with the card. Here, you can either replace the card if it is under warranty or keep it because if the card is running at PCIe 3.0 x8 speed, then the performance loss will be close to negligible (1% to 2% max). In my case, the issue is with the graphics card, which is Gigabyte GeForce GTX 1060 WINDFORCE OC 6G, and I chose to keep it and live with it, because it is not worth worrying and I am getting the full performance out of it, even at PCIe 3.0 x8.
If you have some queries regarding this issue or want to share your opinion and feedback, then you can connect with me using the comment section below.