Does USB use PCIe lanes too?

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dreballs

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Im trying to pick out a Z170 ITX mobo and I was either gonna get the Asrock z170 gaming-itx/ac or the Gigabyte GA-Z170N-Gaming 5 with an i7-6700k, a 980 ti and a Samsung 950 Pro NVMe 256GB utilizing all 20 PCIe lanes that the 6700k offers.

But then I see on Gigabytes site that the Gaming 5's USB 3.1 controller(which supposedly somehow offers 16Gb/s rather than the normal 10Gb/s) uses 2 PCIe lanes. Does this mean that I won't be able to use USB 3.1 since I'll have no more PCIe lanes available? Is this unique to this board? Do the other versions of USB need PCIe lanes too? Can someone please give me the low down!
 
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USB does not use pcie. it uses USB. completely unrelated to your pcie controller.

Your ssd does not use pcie. it uses sata 3.

Your GPU uses a single pcie lane. (rated at 16x speed).

I think that's what you are getting at. sorry if i misunderstood.
 
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no no no Im the one who's misunderstanding things right now. The 6700K supports a max of 16 PCIe lanes. Since most GPUs use 16 PCIe lanes, I surmised that that used up all of the 6700K's PCIe lanes. And since the Samsung 950 Pro is an M.2 NVMe drive that uses 4 PCIe I didn't/dont think the 6700K could support that and a GPU at the same time since it would have no more PCIe lanes to offer? Also according to this site:

http://www.gigabyte.com/products/product-page.aspx?pid=5529#ov

the USB 3.1 controller is using 2 PCIe lanes, which, same thing, can't be supported since theres no more PCIe lanes
 
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The motherboard will likely drop the gpu to 8x to accommodate the additional pcie usage, so it should work and it is unlikely that 8x will bottleneck the gpu for gaming.

Hope this helps!
 
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The speed of your pcie lane doesn't really matter with these new chipsets. (you can run a GPU off a 8x lane fine.)

Each device will only use one lane, of your 16 total.

The GPU for example will only use one lane. it does not use 16 lanes worth of data. the single lane runs at a 16x speed, this does not count towards your pcie limit.

That pcie limit of 16 means it can only handle 16 pcie devices at once, which is WAYY more than your are going to fit onto your motherboard anyways.


You will have no bottlenecks or issues by running an m.2 ssd and a GPU at the same time. they each have their own special lanes to use.

I hope that clears it up alittle.
 
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it will rob graphics lanes available graphics x8 + 950 x4+ 3.1 x2 + Ethernet x1= 15 lanes. x 8 on graphics on pcie 3.0 will not slow graphics fps at all, tested on linus tech tips . M.2 and sata express use more lanes also if used
 
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Ethernet too, eh? Wi-Fi as well? I just saw that Linus video too. With dual GPUs he says that both systems ran the same despite one being being 8x/8x, the other 16x/16x but its pretty clear from the graphs that the 8x/8x 5820k is getting a bit fewer FPS. Is that all CPU variance or what?
 
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Thanks for replying! are you sure? It seems like it would get at least a few less FPS which is what seemed to happen on Linus's PCIe video. He said there was no difference but the graphs showed the 5820k consistently getting a couple less FPS
 
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http://www.techpowerup.com/reviews/NVIDIA/GTX_980_PCI-Express_Scaling/7.html

Here are some interesting benchmarks, the scaling effects I would say would be slightly worse for 980ti as it will likely use slightly more bandwidth but should be similar.

So about 3% fps loss from 16x - 8x at most, some games it seems it doesn't even create any differences. Probably worth the extra use you gain from having the other pcie cards.
 
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First, thanks for the research/reply Partier, but man, I can't believe this. I just can't believe this. I've been researching a build for the last 7 months picking my parts super carefully and now I discover this.... I can't believe Im gonna have to return all my parts, get the only X99 ITX mobo and start over. I don't get this, knowing the reputation of PC users wanting to get the best out of their stuff, how are there so many ITX mobo's for every other chipset except X99? Why are there any non X99 mobo's bigger than ITX? Do people really not care that they are losing performance in SLI? or using ethernet? or USB? or M.2 drives? I don't get it
 
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Hi - Part of the solution may be that the CPU i7 6700 K has 16 PCI-e lanes for the CPU. On Z97 it was the same for the i7 4790K. Again on Z97 there are 8 PCI-e lanes for the chipset. On Z170 chipset there are also PCI-e lanes extra to the CPU but which can only be used for the CPU or the chipset so on Z97 16 CPU + 8 chipset = 24 - Chipset lanes stay on the chipset to power the PCI-e gen 2 x 16 slot for thunderbolt @ x 4 mode or M.2 or Sata Express plus the USB 3 ports blue.

I'll stand corrected if this is not correct. I'm learning about these things but not 100% there yet.

Z170 has more chipset PCI-e lanes than Z97

One idea I'm speculating over is that PCI-e gen 3 always comes off the CPU PCI-e lanes where as PCI-e gen 2 always comes off the chipset PCI-e lanes.

Sata 3 ports 6 Gb/s need PCI-e lanes off the chipset as well - So does LAN which used 1 x PCI-e lane -

If anyone can add to this please do so - I'm searching for accurate facts to assist others and myself as well
 
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