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*SOLVED* Maximus XI Hero (WiFi) only x4 for GPU slot 2

ariesjj
Level 7
I have the Maximus XI Hero (WiFi) set up with the following hardware:
Intel i7 8700K @ 4.9Ghz
4x 16GB RAM (64GB total)F
2x EVGA 1080 SC
2x M.2 2280 drives
2x SSD
ASUS Ryuo 240 AIO
Windows 10 Professional

The issue that I'm running into is that PCIe x16_1 is running at x8 (as expected), but PCIe x16_2 is only showing up at x4. I have gone through the BIOS to ensure that it is recognizing both video cards. Windows is showing both video cards as well and I am able to run in dual monitor setup. However, because (I'm assuming) slot 2 is only x4, I am unable to access the SLI settings to enable it. BIOS is current (0602) and all drivers are up to date. I have also attempted to reseat both GPUs multiple times, swapped slots, cleaned contacts with 91% alcohol, tried multiple SLI HB bridges. I have included GPUz screenshots of both video cards for examination. I could use some extra eyes to help figure out what in the world I am overlooking. Any assistance anyone could provide would be GREATLY appreciated.
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6 REPLIES 6

Tropico
Level 7
I am not an expert but from the manual M.2_2 only operates in PCIe 3.0 x4. M.2_1 slot operates either PCIe 3.0 x4 or SATA (I would say it is currently SATA mode and SATA6G_2 is disabled). This is in the manual page 1-25.

Pity there are only 16 PCIe lanes, really limits 2 x GPU.

ariesjj
Level 7
My M.2 drives are functioning perfectly. It's the PCIe x16_2 (2nd GPU slot) that is only running at x4 instead of the x8 that it is supposed to.

ariesjj
Level 7
To clarify:
PCIe x16_1 is at x8 (Primary GPU)
PCIe x16_2 is at x4 (Secondary GPU) - should be x8 but isn't
PCIe x16_3 is at x4 (M.2 Drives)
SSDs are occupying SATA6G_2 and SATA6G_3

ariesjj wrote:
To clarify:
PCIe x16_1 is at x8 (Primary GPU)
PCIe x16_2 is at x4 (Secondary GPU) - should be x8 but isn't
PCIe x16_3 is at x4 (M.2 Drives)
SSDs are occupying SATA6G_2 and SATA6G_3


OK, the M.2 drives are on a PCIe x16_3 card. ?

I guess it comes down to the argument about whether PCIe x16_3 uses 4 CPU lanes or Chipset lanes.

I am interested to see if you work it out

ariesjj
Level 7
Ok. I located the issue. First to clarify the PCIe configuration for this board. It has 3 onboard PCIe 3.0 x16 slots and 3 onboard PCIe 3.0 x1 slots. Of those slots, 2 of each were populated. x16_1 and x16_2 were populated with my GPUs, x1_1 and x1_2 were populated with Elgato HD60 Pro capture cards. This left x16_3 and x1_3 both unpopulated. My SSD drives were connected to SATA6G_2 and SATA6G_3. Each of the onboard M.2 slots is populated with a 2280 M.2 NVME drive each.

As previously mentioned, both populated SATA6G ports and both m.2 slots were functioning properly. Both of the PCIe 3.0 x1 slots were also performing properly. The issue that was being experienced involved a reduction in speed from x8 to x4 on PCIe 3.0 x16_2. After pouring over the manual, rechecking slot assignments, and looking up PCI lane alotment, I stumbled across the Hyper M.2 footnote. In this footnote, it indicated that when Hyper M.2 (separately sold card) is active, the PCIe 3.0 x16 slots perform in a 8/4/4 configuration. After a good bit of digging in the BIOS, I managed to locate the Hyper M.2 toggle and disabled it. GPU-Z is now showing both drives operating at their expected x8.

Side note: As suspected, now that both GPUs are running at the full x8 the SLI subsection is now displaying in Nvidia Control Panel.

TLDR: Disabled Hyper M.2 in BIOS and resolved issue.

Well done.

Edit: no more need be said