Can't enable x4 on 2nd M.2 Slot

[Travis Simposn]

I have an ASUS ROG Strix z370-i and 2x 1TB Samsung 970Pro in both M.2 slots. I have a 1080GTX in the standard PCIe 16x slot.

Current Specs:
Intel 8700k @ 3.7ghz
Asus Rog Strix z370
2x Samsung Pro 970 1TB
windows 10 Professional in (BIOS Mode UEFI)
NZXT 200i Case
CORSAIR HXi Series, HX1000
Corsair LPX 32GB (2x16GB) 3200MHz C16 DDR4

After testing and downloading the Samsung Magic app I found one of my slots is only running at x1 (where the current installed OS is). I have nothing plugged into any SATA port (so it's obviously not lowering its speed due to a shared drive), and I've gone into the BIOS and completely disabled all SATA drives.

Here is an image from the Samsung Magic app comparing the two drives:

 

[DigitalPanhandler]

im not 100% on this, as I havnt dived into this enough, nor have I upgraded and messed with it my self, but are you sure your cpu can provide the lanes needed?

https://ark.intel.com/products/126684/Intel-Core-i7-8700K-Processor-12M-Cache-up-to-4_70-GHz

• PCI Express Configurations ‡ Up to 1x16, 2x8, 1x8+2x4
• Max # of PCI Express Lanes 16

maybe check and see if your gpu is running x16, and if so try dropping to x8 and see if that allows the second nvme to run x4....

that's just what my logic leads me to think

edit: I should mention, if your gpu was running x16, I imagine none of the nvmes would be able to run x4..... hmmmm

 

[Denpepe]

im not 100% on this, as I havnt dived into this enough, nor have I upgraded and messed with it my self, but are you sure your cpu can provide the lanes needed?

https://ark.intel.com/products/126684/Intel-Core-i7-8700K-Processor-12M-Cache-up-to-4_70-GHz

• PCI Express Configurations ‡ Up to 1x16, 2x8, 1x8+2x4
• Max # of PCI Express Lanes 16

maybe check and see if your gpu is running x16, and if so try dropping to x8 and see if that allows the second nvme to run x4....

that's just what my logic leads me to think

edit: I should mention, if your gpu was running x16, I imagine none of the nvmes would be able to run x4..... hmmmm

The NVMe drives run of the chipset lanes, not the CPU. The chipset should have plenty of lanes (think it's 24 iirc for Z370).

Try using a different app to check as it could simply be an error in magician

 

[DigitalPanhandler]

The NVMe drives run of the chipset lanes, not the CPU. The chipset should have plenty of lanes (think it's 24 iirc for Z370).

Try using a different app to check as it could simply be an error in magician

hmm ok, but I thought that was still dependant on what the cpu could deliver....

but like I said, I havnt upgraded or messed around with it at all...

OP: hope you figure it out and or someone leads you to the correct information


some digging led me to see another person with similar issues.... it appears him swapping the nvme drives around fixed it...

https://rog.asus.com/forum/showthread.php?98258-Z370-E-M-2_2-Only-Getting-PCIe-3-x1

(may or may not be same board, but perhaps just try swapping them..)

 

[Travis Simposn]

Thanks for the help. I still have not been able to fix it even after messing with almost anything in the BIOS resembling something about PCIe or SATA. I might end up being the drive, I'll try swapping them and see what results I get.

I've used a few different hard drive benchmark tools and the secondary drive is significantly faster. The x1 drive was pulling between 700-800 MB/sec while the 4x drive was doing 3100-3200 MB/sec.

Update: I know now it's neither hard drive. I took out each hard drive and put it in the top M.2 socket, both hard drives returned 3X. However the socket that is on the bottom of the hard drive returned 1X (this is the socket that shares resources with SATA) for both drives. In the manual, it says it can be turned off, but I don't know how to do that.

 

[Travis Simposn]

I fixed the issue.

Strangely, my OS drive was installed on the M.2 drive on the back of the motherboard, while my secondary drive was installed in front, where all of the other mobo controls are. However, once I swapped the drives everything was fixed. The OS drive should be on the "top" most socket while a secondary drive can be installed on the reverse side of the motherboard and still run at x4 speed.

 

[Brahmzy]

Strange. I’ve got a bunch of different z370 and z270 ASUS/ROG mobos and it doesn’t matter what or where you put the drives.
The BIOS settings dictate what speeds the M2 slots run at. All combos work @ x4.