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GTX 1080 SLI + M.2 samsung 950 Pro Bottlenck?

Level 7

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.

Level 8
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.

Level 13
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.


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


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


“Two things are infinite: the universe and human stupidity, I'm not sure about the former” ~ Albert Einstein

Level 7
Thank you both for your response. *That clarified a lot for me.