Your PCIe setup should function correctly if all connections and specifications match your requirements.
Your PCIe setup should function correctly if all connections and specifications match your requirements.
Hey, I was always a little confused when it comes to PCIe-lanes and how they work. I'll quickly give you an example of what I'd like to do. Hardware used: AMD Ryzen 9 7950X, ProArt X670E-CREATOR By specification, the Ryzen provides 24 usable PCIe Gen5 lanes and the chipset of the mainboard 12 PCIe Gen4 lanes. The mainboard provides 4 M.2 slots, two of which are connected with PCIe Gen5 and two with Gen4. I also have a simple PCIe Gen4x4 Dante card which I'd like to use. Is it possible for me to populate ALL of those slots at once, regarding that I use 16 lanes for my graphics card already? In theory the lanes provided by processor and mainboard should sum up to a total of 36 lanes. Adding up all the lanes I'd like to use [16(Graphics)+4(M.2)+4(M.2)+4(M.2)+4(M.2)+4(Dante)] I get 36 lanes as well. Will it work?
Based on my research, placing an SSD in M.2_3 usually requires x4 lanes at PCIEX16_3 for a Dante card. If it's already filled, you'll see zero lanes or need to adjust BIOS settings to share lanes between the PCIe slot and the SSD. Swapping to PCIEX16_2 will reduce PCIEX16_1 to x8 lanes, which should work fine for most GPUs, making that a better option if you want to use all available SSDs.
Hey, wow, thank you for this amazing reply! A few quick questions though: Am I going to lose bandwidth if I populate the M.2_3 x2 slot with a PCIe Gen3 SSD? Theoretically the two lanes should have enough throughput for Gen3 speeds but I guess there is no way of converting four lanes of PCIe Gen3 into zwo PCIe Gen4 lanes on an M.2 formfactor, right? Will the SSD (Samsung 970 evo) work at all with only two lanes assigned? And where did those four PCIe lanes go that I am missing?
Significantly half of it, though I’m unsure if the scaling stays perfectly consistent. Not really sure about that. Yes! I tested my 970 Evo in a M.2 slot on an X99 board, which was a first-gen model with just a PCIe 3.0 x2 M.2 port. The only problem was bandwidth loss, handled by the chipset. The CPU supports 24 lanes—16 for main slots, 4 for an M.2 drive (typical), and another 4 for the chipset. All those connections feed back to the CPU with that bandwidth.
You're asking for confirmation about the CPU lane configuration. The information provided indicates 24 usable lanes with a total of 28, meaning four lanes are allocated to the chipset. Your concern seems valid, but the details align with the source you referenced. Thank you for your thoughtful feedback!
It has 28 lanes with 24 usable ports. Anandtech notes most are connected to one of the M.2 slots: https://www.anandtech.com/show/17585/amd...high-end/3. It seems likely there are two M.2 slots linked to CPU lanes.