Nvidia’s GeForce RTX 50 series video cards now support PCIe 5.0. This means that the new graphics have access to an interface that provides twice the speed of interaction with the CPU compared to PCIe 4.0. The TechPowerUp portal, as well as the HardwareCanucks YouTube channel, conducted tests of the new flagship GeForce RTX 5090 card and found out how much performance the card will lose if it is used on motherboards that do not support the PCIe 5.0 interface.
Image source: TechPowerUp
As practice shows, the difference in performance will be barely noticeable if only the card does not work in lines X8, X4 or X1. When using RTX 5090 with PCIe 5.0 support in the PCIe 4.0 X16 Material board, the difference in speed will be only 1 percent. Owners of old motherboards with support only PCIe 3.0 should not be very worried. The average loss of performance in a resolution of 1080p/1440P is 4 %, and when using a resolution of 4K, the loss will be 3 %.
If for some reason the PC has fewer free PCIe lanes allocated to the video card, for example, due to user error, limitations of the motherboard, or due to the use of the video card as an external one, then you should take a closer look at the graphs below.
For example, when using a PCIe 4.0 x4 configuration, which corresponds to the specifications of the OCuLink interface for external video cards, at 1080p resolution the GeForce RTX 5090 card will provide only 89% of its performance (11% loss), at 1440p resolution the card will perform 90% (10% loss) , and in 4K resolution – 94% (6% loss). It should be noted that the card, which costs over $2,000 and is equipped with 32 GB of video memory, is clearly intended not only for games. AI and machine learning enthusiasts who decide to use it as an external accelerator via the OCuLink interface are unlikely to experience a significant performance hit, but more thorough tests using AI/LLM loads are still needed to confirm this claim.
«In general, if you use a platform with the support of the Gen 4 X16 interface, you can relax, because you will lose almost nothing with the GeForce RTX 5090. And any difference from our graphs and your results can be due to the fact that you use more A slow processor compared to our test Ryzen 7 9800x3D. The same applies to users of the Alder Lake and Raptor Lake platforms, who plan to use the GeForce RTX 5090 in the GEN 5 X16 slot, which will only work in X8 mode in the case of installation of the PCIe 5.0 standard, which will eat the remaining PCIe 5.0 lines. If you use the older Gen 3 X16 or Gen 4 X4 interfaces (or by mistakes installed the video card in the wrong slot on the motherboard), you will not see a significant drawdown in performance, but the difference will be, ”writes Techpowerup.
TechPowerUp also reminds you that the GPU-Z utility allows you to check which PCIe interface specification your graphics card uses. The utility also has a built-in test to force the use of full interface bandwidth.
Another thing that should be mentioned in the context of this topic is related to the problem of compatibility of special PCIe riser adapters with modern motherboards. According to HardwareCanucks, whose review focuses heavily on PCIe interface compatibility, some motherboards, when connecting a non-PCIe 5.0 riser to a PCIe 5.0 connector on the motherboard, may require you to manually switch the PCIe settings in the motherboard BIOS to PCIe 4.0 or even 3.0 mode .
Image Source: YouTube/Hardware Canucks
Reviewers have found that users may experience blue screens of death, game loading errors, or even PC boot problems if there are any problems with the riser. This can become a really serious problem, since there are practically no PCIe 5.0 riser adapters on sale, and those that are available are very expensive. As a result, those using PCIe 4.0 and PCIe 3.0 risers may encounter compatibility issues.