[SOLVED] How many free PCI lanes do I have (+ minor related Qs), since want to add M.2 PCI card

Sp3ctre18

Reputable
Mar 1, 2017
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Kind of overwhelmed trying to figure out and understand PCI lanes. Easy to find CPU + mobo chipset lanes, but I don't get how they're taken up, shared, etc.

  1. Is there really no way to just get a report from software? Can't CPU-Z or HWinfo or something else tell me how many lanes in use?
  2. Does CPU-Z's "current link width" under "Graphic Interface" mean the lanes the GPU is using? It says 8x, is that bad?
  3. THE REAL QUESTION: any concerns getting an M.2 PCI card and adding maybe 2 M.2 drives with it? How many lanes will the M.2 drives use?
Thank you!

Components
Gigabyte z170 Gaming 7, Intel i7-6700K, 64 GB ram, Radeon Vega 56
M.2: Samsung 970 1TB, 960 500GB
note: I think 1 M.2 slot is dedicated, other disables SATA ports.
SATA: 3x HDDs, 1x SATA ssd, DVD-RW

PCI slots
3 of 1x, 3 of16x

PCI Cards
GPU
PCIx1 4x SATA card
PCIx1 WIFI
Other
Lots of USB ports in use, incl 3 external hard drives.
 

kanewolf

Titan
Moderator
Thanks, yeah, I remember those details are in there, but is that really all I have to worry about then? Nothing else is using PCI lanes?

(I guess I obviously did forget that when I installed the SATA card though; I have it in an x16 slot for some reason. Should move it to an x1.)

I remember now what also surprises me is that I've seen x1 cards that hold 2 M.2s, but here on my mobo, a single M.2 wipes out an x16!
Full speed M.2 NVMe is an X4 interface. SATA is the equivalent of an X1.
An X1 card with two M.2 cards would be half the speed of SATA.
 

kanewolf

Titan
Moderator
Kind of overwhelmed trying to figure out and understand PCI lanes. Easy to find CPU + mobo chipset lanes, but I don't get how they're taken up, shared, etc.

  1. Is there really no way to just get a report from software? Can't CPU-Z or HWinfo or something else tell me how many lanes in use?
  2. Does CPU-Z's "current link width" under "Graphic Interface" mean the lanes the GPU is using? It says 8x, is that bad?
  3. THE REAL QUESTION: any concerns getting an M.2 PCI card and adding maybe 2 M.2 drives with it? How many lanes will the M.2 drives use?
Thank you!

Components
Gigabyte z170 Gaming 7, Intel i7-6700K, 64 GB ram, Radeon Vega 56
M.2: Samsung 970 1TB, 960 500GB
note: I think 1 M.2 slot is dedicated, other disables SATA ports.
SATA: 3x HDDs, 1x SATA ssd, DVD-RW

PCI slots
3 of 1x, 3 of16x

PCI Cards
GPU
PCIx1 4x SATA card
PCIx1 WIFI
Other
Lots of USB ports in use, incl 3 external hard drives.
The specifications page for the motherboard list what happens -- https://www.gigabyte.com/Motherboard/GA-Z170X-Gaming-7-rev-10/sp#sp
  • 1 x PCI Express x16 slot, running at x16 (PCIEX16)
    * For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
  • 1 x PCI Express x16 slot, running at x8 (PCIEX8)
    * The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.
  • 1 x PCI Express x16 slot, running at x4 (PCIEX4)
    * The PCIEX4 slot shares bandwidth with the M2H_32G connector. The PCIEX4 slot will become unavailable when an SSD is installed in the M2H_32G connector.
The slot closest to the CPU can operate at x16 IF there is nothing in the second slot. If the second slot is occupied then the first slot is also x8.
The second slot is x8
The third slot is x4 and is disabled if the second M2 slot is occupied.
 

Sp3ctre18

Reputable
Mar 1, 2017
12
1
4,525
3
Thanks, yeah, I remember those details are in there, but is that really all I have to worry about then? Nothing else is using PCI lanes?

(I guess I obviously did forget that when I installed the SATA card though; I have it in an x16 slot for some reason. Should move it to an x1.)

I remember now what also surprises me is that I've seen x1 cards that hold 2 M.2s, but here on my mobo, a single M.2 wipes out an x16!
 

kanewolf

Titan
Moderator
Thanks, yeah, I remember those details are in there, but is that really all I have to worry about then? Nothing else is using PCI lanes?

(I guess I obviously did forget that when I installed the SATA card though; I have it in an x16 slot for some reason. Should move it to an x1.)

I remember now what also surprises me is that I've seen x1 cards that hold 2 M.2s, but here on my mobo, a single M.2 wipes out an x16!
Full speed M.2 NVMe is an X4 interface. SATA is the equivalent of an X1.
An X1 card with two M.2 cards would be half the speed of SATA.
 
Sep 9, 2021
5
0
10
0
The slot closest to the CPU can operate at x16 IF there is nothing in the second slot. If the second slot is occupied then the first slot is also x8.
This is a bit confusing because "the slot closest to the CPU" on new boards is actually a Gen 4 M.2 slot. I think this is where a lot of confusion is coming from - for myself included. By taking up this M.2_1 slot (Key M) PCIe 4.0 x4, would you be killing bandwidth of your main GPU by running a

M.2_1
PCIE16_1
PCIE16_2

or

M.2_1
PCIE16_1
PCIE4 (network card)

combo?
 

kanewolf

Titan
Moderator
This is a bit confusing because "the slot closest to the CPU" on new boards is actually a Gen 4 M.2 slot.
You took that statement out of context. It was after the statements from the manufacturer website about PCIe slots. Generally the M.2 near the CPU has dedicated CPU PCIe lanes and does not impact the x16 PCIe slot. A second M.2 PCIe slot will usually have lanes from the motherboard chipset and can impact other functions.
 
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