Bifurcate AsRock x99 Extreme6/3.1


I have read the guide ([Guide] - How to Bifurcate a PCI-E slot by davidm71) and all other threads over the internet for last five days, but still can’t get this to work.

I have 40 lane CPU - Intel Xeon E5 (Broadwell)
Motherboard AsRock x99 Extreme6/3.1
NVMe quad card from Asus

I’m modifying UEFI settings through RU-EFI, but I’m unable to get the quad card do display anything more than one of the NVMe cards in x16 slots.


PCIE1 (Slot 1) - x16 - GPU - IIO 0 / IUO1 - Root Port 3a
PCIE2 (Slot 2) - empty
PCIE3 (Slot 3) - x16 - NVMe - IIO 0 / IUO0 - Root Port 2a
PCIE4 (Slot 4) - empty
PCIE5 (Slot 5/u.2 slot switched) - x8 - empty - IIO 0 / IOU2 - Root Port 1

I have checked my BIOS files and found the IntelSetup variables for modes:
IOU0 - 0x531
IOU1 - 0x535
IOU2 - 0x539

If I put NVMe card in SLOT 5 and set IOU2 to 0x00, I get two drives showing up in my PC, in BIOS, and I can boot from each.
If I put NVME card in SLOT 1 or SLOT 3 and set the IOU1 or IOU0 setting respectively to 0x00, I get only one card; I also tried settings 0x01/0x02/x03, depending on the setting it switched between drives on card, but never shows more then one card at the same time.

In HVINFO with IOU0/IOU1 0x00 setting they show up on PCI Express x4 Bus #2, but for IOU2 0x00 setting they both show up on PCI Express x4 Bus 1.

BIOS: 3.50

Maybe someone can give me any suggestions on what to try or maybe it is a motherboard limitation and I can forget about running more than two cards?

** I’m also fine with running GPU in PCIE2 or x4/x8 modes, if I can push any more lanes towards the NVMe.
*** Sorry I cant post any links.