problems with PCIe and PCIe Express lane distribution
problems with PCIe and PCIe Express lane distribution
I've been exploring the possibility of adding another SSD to my system and believe I'm about to encounter a problem. The plan is to use a PCIe expansion card for the WD_Black SN770 as my gaming drive or the WD_Black AN1500 add-in card, both offering 2TB capacity. But I'm concerned that my current configuration might have already split my PCI Express lanes in a way that prevents proper integration of either device to replace my existing SATA SSD. The motherboard manual suggests the top PCIe slot (PCIe 4.0 x16) is intended for Gen4, 16-lane support, and M.2_1 should work with Gen4 x4 drives. It also mentions that M.2_2 is compatible with Gen4 x4 drives. According to my research, the GPU runs at PCIe Gen3 x8, which aligns with the current setup. However, the GTX1080 seems limited to Gen3 x8 speed according to GPUz. My worry is whether adding a Gen3 x4 or Gen3 x8 card would halve the lanes needed for the GPU, or if I should stick with the existing configuration. Also, I’d appreciate any insight into what might have caused the GPU to drop to Gen3 x8 instead of Gen4.
For heavy storage needs without fully utilizing all SATA ports, an extra SATA SSD works well. The motherboard manual explains how bandwidth is shared across slots (pages 6 and 10 of the PDF). It notes that M.2_1 always has 4 dedicated lanes, while PCIEX16_1 and PCIEX16_2 each receive 8 lanes. If you fill those PCIEX slots, PCIEX16_3 operates at just 2 lanes instead of its full capacity. Placing items in M.2_2 removes ports 5 and 6. You might consider adding a riser into PCIEX16_2 to enable two M.2 SSDs with separate lanes, though this isn't confirmed by the source.
Thank you for your help with this situation. The goal wasn't just about storage capacity but transferring the old Samsung drive into my wife's laptop since it lacks bulk storage. A related update: I've just re-placed the GPU power cables, and GPU-Z now shows a speed of 16, which is great. Regarding the PCIe devices, there aren't any additional ones needed. However, because I resolved the main problem by re-seating the power, inserting the SN770 into slot PCIEX 6_3 should allow it to operate at full PCIe Gen3 x4 speed—enough for my requirements without affecting the GPU.