x399 PCIe slots

hanamichy wrote: Hi, I only have a Radeon 5900 series video card. Because my fan takes up a lot of space, can I install the video card into slot 2 or 3? I'll be using the X399 Taichi. Thanks.

Pay close attention to which PCIe x16 physical slot you use, because they are not all PCIe x16 electrically, if that matters to you. That is, regardless of which PCIe slots are in use or not, the lane allocation per slot does NOT change.

Since all Threadripper processors have the same number of PCIe 3.0 lanes, no need to ask which one you are using.

PCIE1 and PCIE4 are both x16 electrically, and will always provide 16 PCIe 3.0 lanes.

PCIE2 and PCIE5 are both x8 electrically, and will always provide 8 PCIe 3.0 lanes.

But, as has been demonstrated many times, any video card cannot use the bandwidth of 8 PCIe 3.0 lanes, so you could use any of the four PCIe x16 slots without a loss of performance.