4x PCIe Problem on GA-AX370-Gaming K5


Oct 9, 2005
I have a problem with a StarTech PEXUSB3S44V four port USB card on a GA-AX370-Gaming K5 (rev. 1.0) board running Windows 10. I get errors in device manager when the StarTech card is in the left 16x slot. The error is something along the lines of "Windows was unable to reset the device". The StarTech card has four separate USB 3.0 controllers. The error appears on each USB controller. None of the ports are functional when the error is there.

CPU is Ryzen 1700.

This is my understanding of lane allocation according to the manual:
Right 16x Slot - 16 lanes but 8 lanes if middle slot is populated
MIddle 16x Slot - 8 lanes (steals the lanes from right slot)
Left 16x Slot - 4x (shares lanes with 1x slots)
M.2 - no clue where these lanes come from!
1x slots - share with left 16x slot

This works but my GTX0180 is restricted to 8 lanes:
Right 16x - GTX1080
MIddle 16x - StartTech USB
Left 16x - empty
M2 - Samsung 960
1x slots - empty

This produces errors in device manager:
Right 16x - GTX1080
MIddle 16x - empty
Left 16x - StartTech USB
M2 - Samsung 960
1x slots - empty

The StarTech card uses Renesas USB 3.0 controllers. I think they're µPD720202 IC's.

How can I get the StarTech card working in the left slot?
Does the M.2 slot share lanes with the PCIe slots?
Who should I contact to have someone look at this? StarTech or Gigabyte?

I've never seen a problem like this before.

EDIT: MB is on BIOS version F3.
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According to el manual,

(pg 18) The m.2 slot will disable SATA port number 3 if an m.2 SATA card is installed. If it's empty or a pcie (x2 or x4) m.2 card is installed, then all SATA ports will be usable.

(pg 6) PCIEX4 shares bandwidth with the second two pcie 1x slots (PCIEX1_2/3). It operates at 2x when either are populated, or 4x when both are empty.

There should be no issue since all your 1x slots are empty. I'm thinking either something is lodged in that slot, the card isn't aligned in the slot correctly for whatever reason, or there is some hardware/firmware issue preventing proper operation.

I'd shine a flashlight in the slot to verify it's clear of debris and double check the card's alignment after installing it. If it's still not working, contact gigabyte. It could be an issue specific to the startech card, but if it's working fine in another slot, it seems more likely an issue with the motherboard.
Check if there's an option in the bios to select the configuration for the x4 slot. On my motherboard I can manually set it to the mode I want that way