PCIe Lane issue?

[PhysicalVocalist]

So here's the deal,

I've got an i5 6600k and a normal Z170 MOBO with a GTX1070 in my rig right now.  Nothing special, but I want to add a PCIe wifi card to the system.  The only issue is that according to a document from intel I read, my cpu only has support for up to 16 PCIe lanes, and last I checked the 1070 needs all 16 for max performance.  So what I'm wondering is, will adding a 1x card to my mobo cause detrimental effects to my GPU due to a cpu bottleneck?  inb4 "game on ethernet" because I'm in an old ass house that doesn't have ethernet wiring so getting a cable to my office would require drilling holes in the floor or something else janky like that.  

Any wisdom would be appreciated!

[Electronics Wizardy]

you have anouther 24 lanes from the chipset for things like wifi, nic, usb, thunderbolt, raid and other uses. Your fine

 

you can run a gpu at 8x with no performance impact.

 

But for this use the gpu will run at 16x with the wifi card.

[manikyath]

the vareous 1x slots on your mobo are fed by the chipset, not by the lanes the cpu provides directly.

[PhysicalVocalist]

Oh sweet.  That's about as good an answer as I could have hoped for.  What sorts of cards then are controlled by the cpu?  Just stuff like GPUs?

[McHox]

i'm too lazy to get technical so just a short answer:
you'll be completely fine,there shouldn't be any difference in performance

[manikyath]

Just now, PhysicalVocalist said:

Oh sweet.  That's about as good an answer as I could have hoped for.  What sorts of cards then are controlled by the cpu?  Just stuff like GPUs?

whatever you put into the slots that are directly fed by the cpu will be controlled off the lanes directly off the cpu.

 

it's the "obvious choice" for GPU's because less latency and more bandwidth, but for example on very high data troughput enterprise-level servers, they may go as far as to stick those PCIE lanes from the cpu full of network cards.

 

but for pleb-level equipment.. it's pretty much GPU's.

[Mira Yurizaki]

8 minutes ago, PhysicalVocalist said:

Oh sweet.  That's about as good an answer as I could have hoped for.  What sorts of cards then are controlled by the cpu?  Just stuff like GPUs?

Well, all hardware is controlled by the CPU at some point. The point here though is which PCIe lanes feed directly to the CPU and which don't. This is important because the ones distributed by the chipset have to go through a PCIe x4 interface known as the DMI on Intel machines (it's similar on AMD machines). So even if you route 16 lanes from the chipset to the GPU, the effective data rate is PCIe x4 because of it.

 

You might go "but why offer 24 PCIe lanes if the connection to the CPU is only x4?" Because these peripherals aren't hammering the system all the time so you don't need as many lanes. As an example of this class of problem (how many communication lines do you need for a given number of things?), this video provides a very nice one.

In any case, anything that really needs more than 4x PCIe lanes when its running or will need them all the time is something to consider when putting a peripheral in a PCIe slot that routes to the CPU.

[PhysicalVocalist]

So I guess now is the time to ask, how do I know which PCIe slots route directly to the CPU, and which are controlled by the chipset?

[manikyath]

10 minutes ago, PhysicalVocalist said:

So I guess now is the time to ask, how do I know which PCIe slots route directly to the CPU, and which are controlled by the chipset?

the mobo maual will list it *somewhere*

 

but generally, the 16x slots (the reallo long ones) that have a clip thing for holding a card at the back are off the cpu lanes, and the 1x slots (really short ones) or the occasional 2x or 4x physical slots are controlled by the chipset. 

that said, there's a lot exceptions to this rule

[PhysicalVocalist]

Gotcha, thanks guys!!