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  1. #1
    New ROGer Array
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    GTX 1080 SLI + M.2 samsung 950 Pro Bottlenck?

    Hello,

    Sorry if this has been answered elsewhere. I have searched the net for a while and could not get a clear answer.

    Current PC specs
    Mobo: Asus maximus VIII Hero Alpha
    CPU: 6700k
    GPU: Asus GTX 1080 A8G
    SSD: Samsung m.2 950 pro 500gb
    SSD2: Samsung 850 pro 500gb
    SSD3: 1TB western Digital HDD
    Power Supply: 1200 Corsair

    I am looking into adding a second GTX 1080 to run in SLI for gaming. However I am confused with how the MOBO PCIe and cpu lanes work.

    My question I am trying to get answered is:
    Can I run a second GTX 1080 in SLI with and m.2 SSD and not get any bottlenecking in performance from either my 2 GPU's or m.2 ssd? Or will I have to take out my m.2 SSD in order to run GTX 1080 SLI in it's normal full 8x/8x lane capacity?

    My understanding is that the 6700k has a max number of 16 pcie lanes. If each gpu will use a PCIe3x8 lane will that take up all 16 CPU lanes? Further will this mean that there will not be enough pcie lanes available for the m.2 to function at its normal full capacity. Or will the mobo force the GPU1 to run at PCIe3x8, GPU2 to run at PCIe3x4, and the m.2 to run at PCIe3x4 for a total of 16 lanes used? In which case, I'd prob take a performance hit in gaming as the second GPU would not be running at it's normal PCIe3x8.

    Also, as a side note, my GPU-z shows my current GTX 1080 running at PCIe x 16 3.0. Which begs the question, is my m.2 SSD using any pcie lanes at the moment given that the 6700k has a max number of 16 pcie lanes?


    Like I said, I do not understand exactly how all the lanes interact.

  2. #2
    ROG Guru: Yellow Belt Array hiong PC Specs
    hiong PC Specs
    MotherboardAsus Maximus VIII Extreme
    ProcessorIntel i7-6700K
    Memory (part number)F4-3600C16D-16GTZ
    Graphics Card #1Asus Strix 1080
    Graphics Card #2Asus Strix 1080
    Sound CardAsus Strix Raid DLX
    MonitorAsus PG279Q
    Storage #1Samsung 950 Pro M.2 512GB
    Storage #2Samsung 850 Evo 2TB
    CPU CoolerNoctua NH-D15S
    CaseLian Li PC-V2120X
    Power SupplySuper Flower Leadex Titanium 1600W
    Keyboard Logitech G810
    Mouse Logitech G900
    Headset Beyerdynamic T1
    Headset/Speakers Klipsch Quintet
    OS Windows 10 Professional 64-bit
    Network RouterAsus RT-AC88U

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    it is a common misconception that a Z170 system only has 16 PCIe lanes in all. the fact is that it has 36 PCIe lanes in total, 16 from the CPU, and 20 from the Z170 chipset. *the 16 lanes from the CPU is linked to your mobo's first 2 full length PCIe slots, while the 20 lanes from the chipset is linked to the rest of the mobo. *you will have no issues running SLI and a NVMe M.2 SSD concurrently at full speeds.

  3. #3
    Banned Array JustinThyme PC Specs
    JustinThyme PC Specs
    Laptop (Model)G752VY-DH72
    MotherboardRampage VI Extreme
    ProcessorI9 9940X
    Memory (part number)64GB DDR4 8x8 Corsair Dominator Platinum 3800 MHz @ C17
    Graphics Card #1ASUS Strix 2080Ti O11G @ 2.1GHz
    Graphics Card #2ASUS Strix 2080Ti O11G @ 2.1Ghz
    Graphics Card #3ROG Nvlink
    Graphics Card #4Have to feed animals
    Sound CardExternal Audioengine D1 24 bit 192kbps DAC
    MonitorASUS PG348Q @ 100Hz
    Storage #1Intel 905P 480GB U2 flavor
    Storage #2Samsung 850 EVO 1TB X2 in RAID 0, 960 PRO 1TB DIMM.2_1
    CPU CoolerHeatKiller IV PRO and VRM blocks ,Dual D5 PWM serial, 2X 480, 1X 360 RADS
    CasePhanteks Enthoo Elite 8X LL120 PWM, 3X LL140 PWM, 12 SP120 PWM 1x AF140 PWM
    Power SupplyCorsair AX 1500i
    Keyboard ASUS Claymore
    Mouse ASUS Spatha, Logitech MX Master
    Headset Sennheiser HD 700
    Mouse Pad ASUS ROG Sheath
    Headset/Speakers Audioengine A5+ with SVS SB-1000 Sub
    OS Win10 Pro 1809
    Network RouterNetGear NightHawk X10
    Accessory #1 NetGear Prosafe 10GBe Switch
    Accessory #2 Qnap TVS-682 NAS modded with I7 CPU

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    Yep, 16 lanes will go to the PCIe and 20 to the PCH controller.
    The bottom PCIe slot goes through the PCIe controller as does the M2 slot.
    No issues with the M2 slot at all, its just either or with the U2 and who wants U2?

    Here is a diagram of the architecture.
    You cant do the top two slot and run SLI as the second slot is X4 Have to do the Top and 3rd and you get X8 on each.

    Click image for larger version. 

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    As for performance hit, this should show you there are no worries. See specs for machine build on M8E.

    M2
    Click image for larger version. 

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    Firestike Ultra with 2x Srix GTX 1080 A8Gs in SLI using high bandwidth SLI bridge.

    Click image for larger version. 

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  4. #4
    New ROGer Array
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    Thank you both for your response. *That clarified a lot for me.

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