Good day! If using intel core i9-13900k or intel core i9-12900KF processor with Nvidia RTX4090 graphics card, Blackmagic Decklink 8K Pro capture card. These processors have 20 PCI lanes. The video card uses 16 PCI lanes and the Blackmagic capture card uses 8 PCI lanes. In total, 24 lines are required for full operation. But since the processor can work in PCI x16/x0+x4 or x8/x8+x4 mode. Q: How efficient will the system be in x8/x8 mode?
Hi,
There is barely any performance difference between PCIe 4.0 (CPU) x16 and PCIe 4.0 (CPU) x8 lane for video cards, even for RTX4090. However, if you are going to use PCIe 3.0 (CPU) x8, that will probably introduce a significant bottleneck.
You could probably also get away with using Blackmagic Decklink 8K Pro in PCIe 3.0 (CPU) x4. As it seems you are not going to use all the 12G‑SDI slots in their maximum bandwidth of 4k at 60 fps. More on this here: https://forum.blackmagicdesign.com/viewtopic.php?f=3&t=165762
Also, be conscious about what kind of motherboard you buy. For example, in a motherboard specification, the PCIe 4.0 x16 (x4 mode) will mean that the slot has x4 PCIe lanes wired, while the x16 stands for the socket's physical dimensional characteristics.
Warmest regards,
Or recommend a stable workstation configuration to use XR, AR, LED, GreenScreen. The project will be in 4K with 1080 output.