16 PCIe lanes issues

[CapitalistVN]

Hey guys,

I noticed that my core i7-8700K only offered 16 PCIe lanes, and I have 2 GTX 1080 around. I really want to put those cards in SLI, but I know that they use x16 PCIe slot on my Z370 SLI Plus mobo. Are there any problems when I put 2 cards in? Will they work?

[Enderman]

They will run at x8 each which will not affect performance.

[CapitalistVN]

Just now, Enderman said:

They will run at x8 each which will not affect performance.

Isn't that means half the bandwidth?

[Enderman]

2 minutes ago, CapitalistVN said:

Isn't that means half the bandwidth?

8 PCIe 3.0 lanes is more than a GPU uses. There is pretty much no difference between 8 and 16.

[CapitalistVN]

1 minute ago, CUDA_Cores said:

Correct. Assuming OP also has no M.2 SSDs that also need PCIe lanes. Then your GPUs would run at 8x and 4x and nvidia cards won't do that and run in SLI.

So if I add in an M.2 SSD, my 1080 won't run in SLI because the M.2 slot use PCIe?

[CapitalistVN]

Oh thanks guys. See how newbie asks questions?

[NumLock21]

3 minutes ago, CUDA_Cores said:

If you add a M.2 PCIe SSD, your 1080s will stop running in SLI correct. If you add an M.2 SATA SSD your GTX 1080s will continue to run in SLI.

 

If you want to have your cake and eat it too (M.2 PCIe SSD and SLI) you will have to step up to a platform with a higher lane count. This means:

 

1. Buying a mobo with a PLX chip

 

2. Switching to AMD ryzen, threadripper or Intel X299.

 

If you never have a need for an M.2 PCIe SSD however, you have nothing to worry about. 

What?

[SALEEN961]

I think you should be able to run your SLI setup off of the 16 PCIe lanes from the CPU while also running a NVME SSD off of some of the 24 PCIe lanes provided by the Z370 chipset. Your motherboard manual should give you a table showing what's available with different configurations. I know that on mine (Z170) adding a M.2 NVME SSD will turn off some of the SATA ports, but who cares, I still have 4 that work.

 

Looking online at some Z370 board manuals you should be fine so long as your board supports running that many devices and you graphics cards are installed in the correct PCIe slots.