4x NVMe drives paired with a GPU that operates exclusively on the 8th generation (X299 Dark) model
4x NVMe drives paired with a GPU that operates exclusively on the 8th generation (X299 Dark) model
Review pages 27 and 30 of the guide: PCIe-Slot 1 (PE1) provides 16 PCIe 3.0 lanes from the CPU but overlaps with 8 lanes shared by PE2. PCIe-Slot 2 (PE2) offers 8 lanes and also shares another 8 with PE1. PE3 is not usable on 16-lane CPUs, PE4 is not usable on 16-lane CPUs, and PE5 has 4 lanes from the PCH. PE6 supports 4 lanes from the PCH (though physically it shows 16x), activating it will block PE6. Kaby Lake-X supports M.2 Key-M (PM1) with 4 lanes but PE1 won’t load, and PM1 disables one U.2 slot (PU1). PM2 requires M.2 Key-E (PE) with just 1 lane from PCH. The PU1 has 4 lanes from CPU, but PE1 can’t be populated. PU2 is not supported on Kaby Lake X and is disabled on 16 or 28-lane CPUs. The main point is identifying your CPU model and its lane count. Skylake-X seems likely, while Kaby Lake-X probably won’t fit this setup.
I think the BIOS has been updated. Has EVGA released any details about how the lanes are divided with Cascade Lake-X? The manual doesn’t mention anything on that chip. It could be a glitch or there might be a technical explanation. Have you attempted to turn off PM1 and PU1 in BIOS and removed all drives? Noticing you receive 8x performance on PE1 and PE2 suggests the board is likely using shared lanes, which might point to a bug or another reason.
I'm removing everything from that board today, including all NVMes, just to be sure. I updated the BIOS but didn’t get any results. My 2080 Tis were 16x each, and now I can’t even achieve 16x with a single one here. Six months ago I had 2080 Ti SLI, but the motherboard sat unused since then.