MAXIMUS VIII GENE PCIEX4_1 not working

[MikelHerrero]

Problem:

When installing a 16X Graphics card in the PCIEX16/X8_1 bus, the PCIEX4_1 bus does not recognize any installed cards.
Windows informs that the PCIEX4_1 bus is avaible (not occupied) but cannot detect any card installed.
Tried to change in UEFI / Advanced / Onboard devices / PCIEX4_1 from Auto (2X) to 4X (which disables permamently SATA_56) with no success (This test was suggested by ASUS IT crew)
It's not OS relevant. It happens under Windows and Linux.

ASUS IT crew told me to speak with the reseller.

Any idea about it? It is a Faulty Motherboard? or it is its normal way of working instead?

Searched in forums and the official documentation about this motherboard and this case never appears.

[Chino]

What are you installing in that slot for testing?

[MikelHerrero]

I've tested 5 cards

2 different kind of gigabit ethernet cards (intel and realtek) both PCIE 1X
2 different kind of FireWire adapters (VIA and Texas instruments) both PCIE 1X also
1 Serial RS-232 Card , 1X

The motherboard does not recognize none of them

And I run out of ideas of what else to test


I cannot use the PCIEX8_2 because my graphics card is a Zotac Amp! Xtreme! 3-slot 980ti that covers the bus