PCIe lanes confusion

[hoplite.90]

So I got i7-8700k which officially supports 16 PCIe lanes. I am running GTX 1080 in the first PCIe x16 slot and a Tesla K80 in the second slot. My MB is Z370-A-PRO. 

 

I am also running two M.2 NVMe SSDs (one directly, other through PCIe x1 slot), and 2 SATA3 HDDs. As far as everywhere I've read, the M.2 NVMe will take 4 slots from the CPU which does not seem realistic at all. 

 

The screenshots from the BIOS are attached. 

 

The BIOS is saying the GTX 1080 is running in x16 lanes, which is a bit confusing.

The K80 (last screenshot) does not show how many lanes it is running at. It just says PCIe x4 (the MSI Z370-A-Pro has 2 x16 PCIe slots). 

 

I am a bit confused about all of this. What is happening in reality? Are the 1080 and K80 split x8 lanes each? 

 

From what I've seen, it seems like the SSDs and the Tesla K80 are all running through the motherboard's DMA. 

 

What's really going on?

 

 

MSI_SnapShot.bmp MSI_SnapShot_00.bmp MSI_SnapShot_01.bmp

[DejaVoodoo]

Looks like your board only has one x16 slot.  So the second full slot is a x4

 

Aslo:

 

E7B48v1.0.pdf

[hoplite.90]

1 minute ago, DejaVoodoo said:

Yes....if you use a 2nd card in the other x16 slot they become two x8 slots.

 

That was my understanding, but it doesn't seem to be showing that way from the screenshots I've attached. 

[Senzelian]

To be honest, I'm too lazy to look at the specific layout of your board, but this should help to clear things up.

 

16 PCI-e lanes from the CPU
24 PCI-e lanes from the chipset

 

[hoplite.90]

@Senzelian Thank you for the screenshot. That was what I expected, but my BIOS screenshots are still showing something really different. I am wondering if my Tesla K80 is seen as a GPU by the system or as another device type. Because it's showing my 1080 is running at x16 lanes which should not be the case. 

[Senzelian]

2 minutes ago, hoplite.90 said:

@Senzelian Thank you for the screenshot. That was what I expected, but my BIOS screenshots are still showing something really different. I am wondering if my Tesla K80 is seen as a GPU by the system or as another device type. Because it's showing my 1080 is running at x16 lanes which should not be the case. 

@DejaVoodooexplained it with the screenshot he posted.

All PCI-e slots, apart from the first one, run on PCI-e lanes provided by the chipset. So it's all good.

[hoplite.90]

I missed his edit. 

 

@DejaVoodoo thank you for the explanation. What still bugs me is the official specification sheet for the Z370-A-Pro which says: 

 

 

So according to the figure you showed, that only seems to be the physical width of the slot, not the lanes it provides. 

 

Therefore, what I originally assumed stands? The Chipset is the one handling the Tesla K80 instead of the CPU. That explains quite a bit. 

 

On  another matter, the SATA1 port is working fine because I'm not running M.2 SATA SSD, I am running M.2 NVMe SSD in the dedicated M.2 slot. So no issues there.