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PCIe Lane Distribution

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kandiflippin
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2021/08/28 03:23:17 (permalink)
Hey everyone, so I am having some issues setting up SLI for the first time and am a little confused with the PCIe lane distribution. The manual is extremely vague and I am starting to second guess everything I thought I knew about PCIe. I’ll start with the PC specs.

CPU - 10700k
Mobo - Z590 FTW, BIOS is 1.04 (I did just see a new update was released and will update when I’m home)
GPUs - Dual 3090 KPE
Memory - GSkill Ripjaws 2x16gb 3600/cl14
Storage - 1tb Samsung 970 Evo Plus M.2 (Center/80mm slot), 2tb 970 Evo Plus M.2 (Bottom/110mm slot)
Other - Aquacomputer Aquaero 6 and NEXT flow sensor plugged into the USB 3.2 Gen1 port, no SATA devices or any other headers are being used
OS - Windows 10 Home with a fresh install of everything.


Please bear with me as I am still learning and this is my first time having to worry about running out of PCIe lanes. As of right now GPUz is showing GPU1 at x8 and GPU2 at x1.1. From my understanding I should have x16 lanes from the CPU that is only being used by the PCIe slots and x24 PCH lanes for all the various other components. I thought the bottom 2 M.2 slots used the PCH lanes and the top slot used the CPU lanes (with rocket lake). Am I mistaken and these all use the CPU lanes or do I need to start figuring out why I’m not getting the full x16 at the PCIe slots?
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    B0baganoosh
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    Re: PCIe Lane Distribution 2021/08/28 05:06:14 (permalink)
    Did you update your bios? They made some specific improvements for sli.

    You are correct in your understanding that you should be able to run both cards at x8. Did you try reseating them in the slots? (at least tte second one)

    One other thing to consider is that gpuz will show the lane numbers "downclocked" when they are not in use. What does it say in the bios menu?

    Formerly Nike_7688 (please refer to post#77 here for info)

    i9 11900k - EVGA Z590 FTW - EVGA RTX 3080 ti FTW3 Ultra (+Hybrid Kit) - 32GB 3733MHz CAS16 G.Skill, gear1 - WD SN850 2TB NVMe Gen4 - BeQuiet! Dark Base 900 Pro. Project Dark Water MODS RIGS post for build notes.
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    rjohnson11
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    Re: PCIe Lane Distribution 2021/08/28 05:35:25 (permalink)
    According to page 16 and 17 of the manual your PCI-E slots split to 8x when two video cards are installed. 
     
    As an experiment remove the bottom M.2 and recheck GPU2. If you put both NVMe M.2 SSDs into your PC when you installed windows then you might not be able to remove one M.2 at a time. 

    AMD Ryzen 9 5950X,  Corsair Mp600 Pro M.2 2TB, 128GB DDR4  Crosshair VIII Hero, Asus RX 6900 XT Associate Code: H5U80QBH6BH0AXF

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    kandiflippin
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    Re: PCIe Lane Distribution 2021/08/28 05:56:07 (permalink)
    So I just got home from work about an hour ago, just giving a quick update. I just finished updating the BIOS, the BIOS does say 2 PCI devices at x8 3.0. I disabled the top M.2 slot and bottom x4 PCIe slot in the BIOS and started the PC without the NVlink just to see how everything is looking. I’m going to reinstall the latest Nividia driver, do a quick benchmark on each GPU individually, and as long as everything looks fine for each GPU I will power down and reinstall the NVlink.


    B0baganoosh
    One other thing to consider is that gpuz will show the lane numbers "downclocked" when they are not in use. What does it say in the bios menu?


    I was not aware of this so that’s probably where the x1.1 speed was coming from. Thanks for the info on that.
    #4
    kandiflippin
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    Re: PCIe Lane Distribution 2021/08/28 07:46:25 (permalink)
    SLI is now working! Both GPUs worked fine during the individual benchmarks, I installed the NVLINK and as soon as I booted up I got the SLI pop up 😁 I’m assuming the BIOS update fixed it, I do appreciate the info from everyone and for confirming that I was on the right track with understanding how the PCIe lanes functioned.
    #5
    rjohnson11
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    Re: PCIe Lane Distribution 2021/08/28 08:34:27 (permalink)
    kandiflippin
    SLI is now working! Both GPUs worked fine during the individual benchmarks, I installed the NVLINK and as soon as I booted up I got the SLI pop up 😁 I’m assuming the BIOS update fixed it, I do appreciate the info from everyone and for confirming that I was on the right track with understanding how the PCIe lanes functioned.

    Great news. Thanks for sharing. 

    AMD Ryzen 9 5950X,  Corsair Mp600 Pro M.2 2TB, 128GB DDR4  Crosshair VIII Hero, Asus RX 6900 XT Associate Code: H5U80QBH6BH0AXF

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    B0baganoosh
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    Re: PCIe Lane Distribution 2021/08/28 09:09:45 (permalink)
    kandiflippin
    So I just got home from work about an hour ago, just giving a quick update. I just finished updating the BIOS, the BIOS does say 2 PCI devices at x8 3.0. I disabled the top M.2 slot and bottom x4 PCIe slot in the BIOS and started the PC without the NVlink just to see how everything is looking. I’m going to reinstall the latest Nividia driver, do a quick benchmark on each GPU individually, and as long as everything looks fine for each GPU I will power down and reinstall the NVlink.


    B0baganoosh
    One other thing to consider is that gpuz will show the lane numbers "downclocked" when they are not in use. What does it say in the bios menu?


    I was not aware of this so that’s probably where the x1.1 speed was coming from. Thanks for the info on that.


    I learned that here, so I was happy to pass it along.

    Formerly Nike_7688 (please refer to post#77 here for info)

    i9 11900k - EVGA Z590 FTW - EVGA RTX 3080 ti FTW3 Ultra (+Hybrid Kit) - 32GB 3733MHz CAS16 G.Skill, gear1 - WD SN850 2TB NVMe Gen4 - BeQuiet! Dark Base 900 Pro. Project Dark Water MODS RIGS post for build notes.
    #7
    Kasque
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    Re: PCIe Lane Distribution 2021/09/24 06:48:31 (permalink)
    i am happy to hear it, i just need to get that last gpu card and i'll be able to use it for the SLI compatibility !
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    zippytek
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    Re: PCIe Lane Distribution 2021/10/01 08:11:14 (permalink)
    kandiflippin
    SLI is now working! Both GPUs worked fine during the individual benchmarks, I installed the NVLINK and as soon as I booted up I got the SLI pop up 😁 I’m assuming the BIOS update fixed it, I do appreciate the info from everyone and for confirming that I was on the right track with understanding how the PCIe lanes functioned.



    love to see it. i've got dual kingpins in my bench as of last night finally. but i'm not even seeing the SLI setting in nvidia control panel. additionally, i see both cards as x8 though i just have 1 nvme in the middle slot on 10900K. in your opinion, do I need to update my bios as well? i'm on z590 dark so not sure if the issue is similarly resolved with a bios update.
     
    thanks for any help you can offer! have a great weekend

    Update: I flashed the newest bios for the board and we are in business.

    First non stock PR: https://www.3dmark.com/3dm/66749347
    post edited by zippytek - 2021/10/01 21:18:25
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