How do PCIe lanes work with the cpu & motherboard chipset?

[Telekino]

I am confused about how the lanes work. This is a diagram of the motherboard I want to get.

http://techreport.com/r.x/2015_9_19_Gigabytes_Z170XGaming_7_motherboard_reviewed/05-diagram_pcie_routing.gif

I may eventually use 2 graphics cards in SLI. If my cpu has 16 lanes, can I use the PCIe that are part of the motherboard chipset (the light blue), or do the graphics cards take up all the lanes on the motherboard? Could I install an M.2 PCIe ssd and run 2 graphics cards in SLI?

 

[kanewolf]

That diagram says that the motherboard has three slots that are PCIe x16 in physical size. If you use the first one ONLY it gets 16 lanes. If you use slots 1 and 2 they get 8 lanes. If you use the third slot it gets 4 lanes as long as you don't have an M.2 drive in one slot.

You can run two graphics cards each getting 8 PCIe lanes and an M.2 (actually 2 M.2) drives.

 

[junkeymonkey]

well I guess the thing to do is look at reviews that cover the slots on the board your look at ?? if there is one out for it ?

example
http://www.hardwaresecrets.com/gigabyte-z170x-gaming-7-motherboard/2/

now as you see the disabled part ?? so with all the lanes that are in the chipset why are they not shared or ''wired'' to it ?? so its shared with the cpu and not with the chipset .. thing is if its disabling things through the cpu then why not fully put it on the chipset unless its a full 8x requirement ??

''The third PCI Express 3.0 x16 slot works always at x4 speed, and it shares its lanes with the second M.2 slot. So, if the second M.2 slot is used by a PCI Express SSD, this third PCI Express 3.0 x16 slot will be disabled.''

so you got to see how there set up from the manufacture -

 

[Telekino]

I think I understand now. 16 lanes are used by the graphics cards (in SLI at 8x each for a total of 16), and 4 lanes are used by the M.2, for a total of 20 lanes being used.

However, the CPU only has 16 lanes. Can a CPU that has 16 lanes run a system that uses a total of 20 lanes? (I think 16 lanes are being controlled by the CPU, 4 lanes are being controlled by the motherboard, so it would be okay?)

 

[junkeymonkey]

did you not see the part about disabled above ???

16 lanes don't mean you can run 20 ??

you got 16 on the chip that's shared or you got lanes shared ''wired'' to the chipset [say the 170 chipset has its own 24 lanes ]

AMD its all through the chiposet

 

[kanewolf]

I think I understand now. 16 lanes are used by the graphics cards (in SLI at 8x each for a total of 16), and 4 lanes are used by the M.2, for a total of 20 lanes being used.

However, the CPU only has 16 lanes. Can a CPU that has 16 lanes run a system that uses a total of 20 lanes? (I think 16 lanes are being controlled by the CPU, 4 lanes are being controlled by the motherboard, so it would be okay?)

Yes a CPU with 16 PCIe lanes has additional connectivity to the motherboard infrastructure. The motherboard has another 18 lanes. Even if you had only a single graphics card and nothing else, you would be using more than 16 lanes because the network uses some and the SATA and USB use them.

 

[junkeymonkey]

that storage is through the chipset the chip is the slots one card full 16 2 cards 8x8 3 cards 8x4x4 3 cards the m2 is disabled as wired through the slots on the cpu any combo cant exceed 16x on the cpu

now if you go with a 'X'' board that has a plx chip on it then things change that forces sharing with the chipset lanes

thing I guess to look at does the board offer a extra m2 that's ''wired'' through the chipset as well ?? then your kinda covered

 

[mechpro1]

well I guess the thing to do is look at reviews that cover the slots on the board your look at ?? if there is one out for it ?

example
http://www.hardwaresecrets.com/gigabyte-z170x-gaming-7-motherboard/2/

now as you see the disabled part ?? so with all the lanes that are in the chipset why are they not shared or ''wired'' to it ?? so its shared with the cpu and not with the chipset .. thing is if its disabling things through the cpu then why not fully put it on the chipset unless its a full 8x requirement ??

''The third PCI Express 3.0 x16 slot works always at x4 speed, and it shares its lanes with the second M.2 slot. So, if the second M.2 slot is used by a PCI Express SSD, this third PCI Express 3.0 x16 slot will be disabled.''

so you got to see how there set up from the manufacture -

This Lanes business confuses me too. Can anyone offer any clarification on the following sentence from that article: "The third PCI Express 3.0 x16 slot works always at x4 speed, and it shares its lanes with the second M.2 slot. So, if the second M.2 slot is used by a PCI Express SSD, this third PCI Express 3.0 x16 slot will be disabled.
Read more at http://www.hardwaresecrets.com/gigabyte-z170x-gaming-7-motherboard/2/#tCtQYYflhSlJeYVl.99"

Why is the third PCIe 3.0 slow referred to as an x16 slot if it always runs at x4 speed (meaning always utilizes four lanes)?

 

[kanewolf]

well I guess the thing to do is look at reviews that cover the slots on the board your look at ?? if there is one out for it ?

example
http://www.hardwaresecrets.com/gigabyte-z170x-gaming-7-motherboard/2/

now as you see the disabled part ?? so with all the lanes that are in the chipset why are they not shared or ''wired'' to it ?? so its shared with the cpu and not with the chipset .. thing is if its disabling things through the cpu then why not fully put it on the chipset unless its a full 8x requirement ??

''The third PCI Express 3.0 x16 slot works always at x4 speed, and it shares its lanes with the second M.2 slot. So, if the second M.2 slot is used by a PCI Express SSD, this third PCI Express 3.0 x16 slot will be disabled.''

so you got to see how there set up from the manufacture -

This Lanes business confuses me too. Can anyone offer any clarification on the following sentence from that article: "The third PCI Express 3.0 x16 slot works always at x4 speed, and it shares its lanes with the second M.2 slot. So, if the second M.2 slot is used by a PCI Express SSD, this third PCI Express 3.0 x16 slot will be disabled.
Read more at http://www.hardwaresecrets.com/gigabyte-z170x-gaming-7-motherboard/2/#tCtQYYflhSlJeYVl.99"

Why is the third PCIe 3.0 slow referred to as an x16 slot if it always runs at x4 speed (meaning always utilizes four lanes)?

Because a x16 card will physically fit in the connector. But there are only x4 data lanes in that slot.

 

[junkeymonkey]

the slot as hardware is x16 but it can run at any pci-e speeds as said above that one slot is allocated for x4 and shared with the m2 through the chipset lanes [on intel the most part the cards use pci-e slots run through the cpu ! slot =x16 speed then if say 2 used for sli there split to x8 and x8 speed that then equals the cpu's x16 ] only the slots meant for graphic card use is wired to the cpu the rest of the slots most times are run through /shared through the chipset [AMD cpu's don't support pci-e lanes built in as intel and all are run through/shared through there chipsets

https://en.wikipedia.org/wiki/PCI_Express

thing is there only so much lanes to be used and like with NVidia cards they require a min.x8 on the slot where amd cards can run as low as x4 slot

and the same for any hard ware you install so if you use 2 m2 cards your out od lanes then something got to give them up so the slot is disabled to support that deal .

so it eather the 1 m2 and the sklot or the slot or 2 m2 cards theres only so much to go around and a cpu/chipset limitation on z boards

now if you look at x boards they go up to something like 40 lanes with there plx chip and that limitation is not there I assume ? [what I said above ]