[SOLVED] m.2 port running at x2 instead of x4

[Ronnie30]

Hi,

I just picked up a new Samsung 970 Evo Plus 500gb NVMe drive and all benchmark tests are running at roughly half speed. According to the Samsung Magician software, I'm running on PCIe Gen 3x2, but the motherboard (GA-Z170x-UD5 TH) manual says that the m.2 shares bandwidth with the PCIe x4 slot, and only one of those 2 (m.2 or pcie x4) can be used, which leads me to believe this is actually an x4 m.2 slot.

Speccy indicates that I have a x16 PCIe slot, and 4 PCIe slots running at x1, when in fact I should have an x16, x8 and an x4, and 2 x1 slots. I ran SiSoftware Sandra which shows this as a PCIe 3x2 slot as well.

The manual does have some info about supported configs with SATA ports (see here), but I didn't think they shared bandwidth.
Can anyone confirm that this should in fact be an x4 m.2 slot, or what might be causing it to run at x2, please?

 

[kerberos_20]

it is x4 slot 32G means 32gigabit (which is 4GB/s)
see your bios settings if there isnt setting for lanes there

 

[kerberos_20]

so it seems its gigabyte bug
https://forum.gigabyte.us/thread/4183/z170x-samsung-970-nvme-speeds
feel free to contact theirs support

 

[Ronnie30]

Thanks. I have raised a ticket with them, but the response they gave to one of the posters in your link, doesn't fill me with confidence. Fairly certain my bios settings are already correct but I'll double check on next reboot.

In that link, someone wrote "The only sharing that occurs with these boards is that the M.2 slot under the gpu will disable the bottom (x4) pcie slot, and you will lose some sata slots depending on what type of M.2 card is installed in a slot. "

That's not my board they are talking about, but it's the same port. I've got 4/6 of my sata ports in use. Could this be affecting it, or would it completely disable the sata port?

 

[Ronnie30]

BIOS was set to auto, so I set it to Gen 3. Also updated to the latest bios.
It's now showing as Gen 3 x4 and benchmarks are reporting much better results (still lower than I was hoping but near double what it was previously). Thanks