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MOBO SLI PCI-E lanes

I have an ASUS x99-A II Mobo with intel broadwell-e 6580K CPU with 40 PCI-e lanes, GTX 1080 in SLI, and Intel 750 PCI-E SSD 1.2 TB.

My issue is that GPU 1 is running at 3.0 x8 lanes and GPU 2 running at 3.0 x16 lanes, despite having enough PCI-e lanes from the CPU.

GPU 1 installed in PCI-E_1 slot and GPU 2 installed in PCI-E_3 slot per factory instructions, both slots rated PCI-e 3.0 x16 lanes.

The SSD is installed in the PCI-E_4 slot, also rated at 3.0 x16 lanes, but the SSD is only supposed to be using up 4 lanes
5 answers Last reply Best Answer
More about mobo sli pci lanes
  1. Go into BIOS Advanced Mode and look for GPU post and see if it offers changes.
  2. Zerk2012 said:
    Go into BIOS Advanced Mode and look for GPU post and see if it offers changes.


    No changes offered

  3. Best answer
    it got a note on spec https://www.asus.com/us/Motherboards/X99-A-II/specifications/
    1* PCIe x16_1 and PCIe x16_4 slots share the same bandwidth. PCIe x16_4 slot support up to x8 mode.

    try moving your ssd
  4. This sucks! The only other one left is PCIEX16_2 slot sandwiched between the GPUs which only runs Gen 2.0 plus shares bandwidth with a couple other features and the SSD needs Gen 3.0. Thanks for the help anyways guys.
  5. Hey would you guys happen to know if x8/x16 SLI has a significant performance drop compared to x16/x16 or x16/x8 or x8/x8? Or does the order even matter if they're not equal?
    My true concern is since the primary GPU is running at x8 lanes then even games that aren't using SLI will be limited to x8 lanes whereas the secondary GPU won't even be used with its x16 lanes! I just never encountered the FIRST slot on a motherboard to share bandwidth with anything else, kinda bummed out about it
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