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Not enough PCIe lanes?

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I am currently tossing around the idea of building a computer to run VR games. (I'd probably game in Windows and do everything else in Mac, but that's not important) I plan on getting a GTX 1080 once it's available (if it works with OSX). I want to make the computer at least a little bit future-proof, so I was considering leaving room to add a second GTX 1080 in SLI if the need arises down the line. The problem is that the latest generation of Intel processors only have 16 PCIe lanes, and to run in SLI, each card needs 8 lanes, leaving no room for any other PCI devices, like an M.2 SSD.

Should I instead get a slightly slower 5th-generation processor that has 28 PCIe lanes, or would I be better off just getting a new single graphics card once the 1080 is outdated? Or am I just seriously overthinking this?
 
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Dont Z170 boards have PCI lanes via the chipset, not the CPU, so the PCIx16 GPUs wont step on the CPU lanes?
 
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I guess that's part of my problem: I have no idea what you're talking about. Are you saying that the motherboard can essentially add more PCIe lanes, so I'm not just limited to the 16 of the CPU?

I should specify that I've never actually built a computer before, so this is all new to me.
 
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In case anyone else is wondering the same thing, I've done some research, and here's what I found: The CPU has 16 PCIe lanes, which are used pretty much exclusively for the graphics card(s). A given motherboard might have some PCIe slots hardwired to the CPU. (The specific motherboard I'm looking at does, at least). The chipset on the motherboard also has some PCIe lanes (the Z170 has 20), used for anything else that requires PCIe. The motherboard manufacturer can use those lanes as they see fit; for example, for M.2 connectors or SATA express. The chipset, and therefore indirectly these additional 20 lanes, are then connected to the CPU through some other sort of connection that doesn't really matter since it's the same for every motherboard.

So in summary: The CPU has 16 PCIe lanes for graphics cards, and the chipset on the motherboard has an additional 20 lanes, which can be used for M.2, SATA express, and PCIe cards that aren't as intense as graphics cards. (Like a networking card)
 

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In case anyone else is wondering the same thing, I've done some research, and here's what I found: The CPU has 16 PCIe lanes, which are used pretty much exclusively for the graphics card(s). A given motherboard might have some PCIe slots hardwired to the CPU. (The specific motherboard I'm looking at does, at least). The chipset on the motherboard also has some PCIe lanes (the Z170 has 20), used for anything else that requires PCIe. The motherboard manufacturer can use those lanes as they see fit; for example, for M.2 connectors or SATA express. The chipset, and therefore indirectly these additional 20 lanes, are then connected to the CPU through some other sort of connection that doesn't really matter since it's the same for every motherboard.

So in summary: The CPU has 16 PCIe lanes for graphics cards, and the chipset on the motherboard has an additional 20 lanes, which can be used for M.2, SATA express, and PCIe cards that aren't as intense as graphics cards. (Like a networking card)
Incorrect,
First thing you do is look at the CPU specs at http://ark.intel.com/
For my i7 5930K, for example, http://ark.intel.com/products/82931/Intel-Core-i7-5930K-Processor-15M-Cache-up-to-3_70-GHz says I have a max of 40 PCIe 3.0 lanes. An i7 5830K has only 28 lanes.
Then you look at the mainboard specs at your OEM site.
For my Asrock X99M Killer, for instance, under expansion/connectivity - slots, it says I can run PCIe3.0 slot 1 and PCIe3.0 slot 2 at X16 mode if I buy the 40 lane CPU, but I am limited to X16 on PCIe1 and X8 on PCIe2 if I use the 5820K since it only has 28 lanes available on the CPU. I also have 1 PCIe2.0 x4 slot and the M.2 slot is a PCIe3.0 x4.
An x16 capable GPU will run at x8 or even at x4 which is what allows you to have 4 GPUs populating all of your slots for SLI or Crossfire - the system will recognize the presence of the device in the slot and allocate lanes automatically.
 
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Alright then once again I don't understand. I'm looking at an MSI Z170A Gaming M5, which has the LGA1151 socket of 6th-generation intel CPUs, all of which have only 16 PCIe lanes. (source) The motherboard will support dual graphics cards in SLI, which, by NVIDIA's specifications of SLI, absolutely requires each card to have at least 8 lanes (Even though a single card can operate with fewer than 8 lanes, NVIDIA requires that, for SLI to work, each card must have at least 8 lanes)(source), which takes up all 16 lanes of the CPU. However, the motherboard also has 2 M.2 slots and 2 SATA express slots, all of which require PCIe lanes, and everything I've read seems to indicate that I can use two graphics cards in SLI, and also use those M.2 or SATA express slots, which seems to conflict with what you said. (source, although I guess it didn't explicitly say that I could use all of that at the same time. It just didn't mention that that was an issue)

And also, this block diagram of the Z170 chipset seems to agree more with what I was thinking than with what you said. The CPU has 16 PCI lanes attached to it, and then the chipset has an additional 20 PCI lanes. The chipset seems to act kind of like a USB hub for PCIe lanes, by switching the traffic through those 20 lanes through that DMI 3.0 link.

z170-chipset-block-diagram-rwd.png


Like I said, this is all new to me, so I'm not doubting that you know more about this stuff than me, but I just want to know where I'm wrong so I don't make this mistake again in the future.
 
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Does not conflict - what I said was add them up and used my hardware as an example.
How many does the CPU provide from the GPU core? For your sample CPU = 16 lanes
How many does the CPU provide from the PCH chipset? For your sample PCH = 20 lanes.
What does the OEM mainboard support? For your sample, either 1 GPU @ x16 lanes or 2 GPUs @ x8 lanes each or 3 GPUs - 1 @x8 and 2 @ x4 lanes each. Note that the M.2 PCIe x4 slot for the SSD and the SATA express ports uses only the PCH lanes, not the GPU lanes. The GPUs are not capable of using the PCH lanes.
 
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Well there seems to have been a miscommunication because now we're saying the same thing. Sorry about that. Glad we could come to an agreement, I guess.
 

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Well there seems to have been a miscommunication because now we're saying the same thing. Sorry about that. Glad we could come to an agreement, I guess.
My hardware may not have been a good example as my CPU does not have a GPU core. All of my lanes are from the CPU.
 
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