Skylake running 2x PCIe 3.0 SLI, m.2 ssd PCIe x4, network card x1

blim10 · Aug 4, 2016

Hi guys,

Planning to build my new Skylake PC but confused on PCIe lane availability and all the stuff I want to run.

Current Specs:
- i7 6700K
- samsung 950 m.2
- network card x1
- GTX 1070
mobo: Asus Z170 AR

So far I only have the one GTX 1070 to run along with the other components. But I want a little flexibility installing a second 1070 into the mobo at a future date. Skylake has 20 PCIe lanes so: 4 taken by the ssd, 16 by graphics card (8x, 8x) thats all 20 used up without the network card.

My question is, how would I install the x1 network card with no pcie remaining or how would it affect the motherboard by installing it anyway?(i.e. what performance degradation would it have on the graphics cards? (forced to run at x4, x4?)

Thanks guys,
can't seem to find this anywhere for my setup.

BurgerandChips66 · Aug 4, 2016

I have a system with the ASRock Z170 OCF and an i7 6700K.

I recently added a second graphics card and decided to connect up as follows: -

2 x graphics cards installed on PCIe running @ X8 (R9 Fury and R9 380X)

1 x WIFI adapter installed in PCIe X1 slot

2 x SSDs via SATA III

I ran benchmarks of both the cards (individually) at full X16 speed and later at X8 speed to check and discovered a performance drop of just 0.1% and 0.13% for each card.
In games so far this has not equated to any drop in performance I can observe. Arguably it is within experimental error. Basically PCIe 3.0 is so fast that running a card in X8 mode doesn't cause any issues atm.

You could alternatively use a USB WIFI adapter instead of a PCIe adapter or just connect a wireless router to your PC via the LAN RJ-45 port - if for some reason you don't want to use a USB WIFI adapter.

Samer1970 · Aug 4, 2016

blim10 :

hello ,

The Graphic card slots 8x , 8x take their lanes directly from the CPU and not the 20 lanes of the chipset .

The CPU has 16 lanes ..

you still have 20 lanes unused from the chipset .

but you need to know which slot is connected to the chipset lane and which slots are connected to the CPU lanes ..

the SLI/CF 16x slots are connected to CPU

all the others , M2 , SATA , USB , LAN , and x1 , x4 , x8 other slots are connected to the chipset ..

keep in mind that the DMI 3.0 bandwidth limits the total bandwidth of the 20 lanes from the chipset ... the DMI 3.0 is actually 4 lanes only so the cards on the 20 lanes will never run 20 lanes for real if all lanes are used at the same time and at load all of them.
if you want real lanes bandwidth go for X99 motherboard , the CPU has 40 lanes .. but only if you need that .

blim10 · Aug 24, 2016

[/quotemsg]

hello ,

The Graphic card slots 8x , 8x take their lanes directly from the CPU and not the 20 lanes of the chipset .

The CPU has 16 lanes ..

you still have 20 lanes unused from the chipset .

but you need to know which slot is connected to the chipset lane and which slots are connected to the CPU lanes ..

the SLI/CF 16x slots are connected to CPU

all the others , M2 , SATA , USB , LAN , and x1 , x4 , x8 other slots are connected to the chipset ..

keep in mind that the DMI 3.0 bandwidth limits the total bandwidth of the 20 lanes from the chipset ... the DMI 3.0 is actually 4 lanes only so the cards on the 20 lanes will never run 20 lanes for real if all lanes are used at the same time and at load all of them.
if you want real lanes bandwidth go for X99 motherboard , the CPU has 40 lanes .. but only if you need that .[/quotemsg]

Thanks for replying guys.
Ahh okay, so now I know that GPU lanes are linked only to the CPU (depending on the slot type of course). So essentially, 20 lanes are in the chipset itself and that's for everything else. Also, I didn't understand what you meant by
[/quotemsg] the DMI 3.0 is actually 4 lanes only so the cards on the 20 lanes will never run 20 lanes for real if all lanes are used at the same time and at load all of them. [/quotemsg]

Can you please clarify?

Samer1970 · Aug 24, 2016

Meaning if your card you are using connected to the chipset is using more than 4GB/s will be bottlenecked by the Chipset DMI3.0 to CPU connection it will never go above 4GB/s .

but if you use the same card on CPU lane it will not be bottleneck...

keep on mind everything in the chipset uses this link as well , SATA3 , USB3 , Cards etc .

blim10 · Aug 30, 2016

Samer1970 :

Ahh ok, gotcha. Thanks a lot for that.

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Skylake running 2x PCIe 3.0 SLI, m.2 ssd PCIe x4, network card x1

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