NVIDIA's flagship GeForce RTX 5090 is over 25% slower without full PCIe bandwidth

NVIDIA's flagship GeForce RTX 5090 loses over 25% of its performance in professional video editing workloads when it isn't fed its full PCIe bandwidth in new testing.

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The folks over at Puget Systems have tested the GeForce RTX 5090 to see what performance impact there is when the card is under limited PCIe bandwidth, as there are situations in particular systems when this is a major issue. Some users may have the RTX 5090 inside of a system that has another add-in card that is using those precious PCIe lanes, and that reduces the performance of the GPU.

Puget Systems started the testing with After Effects where the RTX 5090 loses a large chunk of performance when the GPU drops from PCIe 5.0 x16 to PCIe 3.0 x4 with over 10% performance loss, while the same performance loss is noticed with DaVinci Resolve where over 20% performance is lost when the GPU is running in PCIe 3.0 x4 with performance also being lost when the number of lanes is dropped from x16 and x4 in the same Gen5 slot. This means multiple AICs on your motherboard can definitely have a huge performance impact on the RTX 5090.

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In Game Dev benchmarks like Unreal Engine, performance loss between PCIe configurations isn't anywhere near as great, including AI workloads. Puget Systems tested things like the Llama.cpp benchmark, where there wasn't a performance impact when lower PCIe bandwidth was fed into the RTX 5090, which is because there's not much of a performance loss because these apps are more dependent on the VRAM of the GPU.

Gamers won't need to worry about this, but professionals and content creators need to be aware of PCIe bandwidth issues, so they'll need to be careful of which CPU and motherboard they're using. Using a high-end professional CPU and motherboard like an AMD Ryzen Threadripper CPU can reduce (and even remove) these potential bottlenecks, as there are plenty of PCIe lanes for multiple GPUs, AICs, and more.