Tried using grub to edit the BIOS and changed the correct variable for IOU0 (IIO PCIe Port 2) and IOU0 (IIO PCIe Port 3) for to be 00 for x4x4x4x4
And still nothing
I also modified the BIOS and changed the first line so i can use flashback
not sure what I am doing wrong…
I have tried setting both Failsafe and Optimal to x4x4x4x4 and attached .zip has only the optimal to x4x4x4x4 and still windows and BIOS only see the card as x4
STXX99MOD3.zip (7.3 MB)
Ok forget about AMIBCP…i dont have time for this.
Just follow the presented guide please, its all well documented.
1 Like
asus x99-e ws bifurcation bios. Has anyone met with this?
You need 5 and 7 PCI e 16 slots. Redo it to 4x4x4x4. If anyone has a modified bios, please contact me.
Hi, I am a new comer. I just want to say thank you to the author of this thread, for teaching how to Bifurcate the PCI-E slot by BIOS mod. I follow the guide and it works!
I can confirm Asrock Rack D1541D4U-2T2R can make bifurcate of the 2 PCIe buses (physically one long and one short, but electrically they are both 8x PCIe 3.0) . The bifurcation setting just hidden and can be enabled by easily mod of the BIOS. I tested by a 2 slot M.2 to PCIe adapter.
The method is here:
- Use AMIBCP to load the BIOS, find the IntelRCSetup → IIO, change “PCIe4 link width” , “PCIe6 link width” and “IIO0 Configuration” Access/Use to “USER”.
- Save, flash the BIOS
- Go into the BIOS and find the option, change to “x4x4” and “x4x4x8”
- Enjoy.
modded BIOS can be download here (DO IT AT YOUR OWN RISK):
1 Like
Hi Charles,
nice to know somone managed to activate bifurcation on Rampage 5 Extreme.
Do you by any chance performed that to stock 4101 as well?
I’d really like to try out both, if you’d like to share your mods.
Thanks in advance and with kind regards
Matthias
Hi, and welcome to forum!
I followed this tutorial on my ASRock X99 Extreme4 with Xeon E5-2697v3 and I’m starting to lose hope, that it would ever start to work. Tried multiple combinations, but couldn’t get to work more than one NVMe drives in 4x M.2 adapter to PCI-E. Have 3 drives (Kioxia Exceria G2, Plextor M9PGN+, Samsung 970 Evo Plus). Plextor is in built-in M.2 slot, Kioxia in 1st adapter slot and Samsung in 2nd. Attached screen how it’s plugged in.
Already modded BIOS with AMIBCP and flashed modified BIOS with AFUDOS. Using RU to modify values that are responsible for bifurcation, attached in the screen.
Thing is, that setting value to 00 does… literally nothing, only 1st drive in adapter is detected. Tried the same thing for testing on slot where GPU is, and looks like it worked correctly, as GPU switched to use 4 lanes only. The more interesting thing is, that when I switched value to 03 (that’s x8x8)… only second drive in adapter is detected, other M.2 slots become inactive, though tried to populate 2nd and 4th slot (and various other combinations)
Tried also:
Swapping out the M.2 adapter into Port 3 - same thing happens
Leaving the built-in M.2 empty and trying 3 drives in adapter - still no luck, only one drive available at the time.
Really hoping, that I missed something trivial or there is some other method to bifurcate the slot 
All screens/photos: Imgur: The magic of the Internet
Thanks in advance for help!
Anyone has any idea whether this would be possible on an ASRock H110M-ITX/AC?
Hello david and to everyone aswell 
I don’t understand the part where you find the address on RU,
From what I understand in X53C the value is this right?
05 91 BE 04 C7 04 83 02 01 00 3C 05 10 10 00 FF 00
But from what I see in ur RU setup you are editing a bunch of 0 and 1 like 00 00, did you use a tool to convert this “05 91 BE 04 C7 04 83 02 01 00 3C 05 10 10 00 FF 00” into bunch 0 and 1?
Or can you help me, do this mod? I already have the strings extracted using ifr extraction tools
This worked for me on one of those Chinese ‘X99’ Matx boards. Many thanks
Desktop motherboards need special attention and are generally limited to x8x4x4, assuming vestigial support for x8/x8 or x8/x4/x4 graphics or ‘hyper M.2’. check owners manual for any mention of that. Open BIOS with a tool and look for the options.
Chances very low, practically non-existent.
Hi there, I got it working on my Asus X99 Deluxe II but not via BIOS mod (still working on that)
I applied the RU settings changes via EFI Shell, the addresses to mod for PCIe16_3 (4th slot) IOU0 are 0x533 0x534 0x535 0x536, set them from FF to 00
My Quad m.2 running RAID0 in Windows
BIOS modding hasn’t worked yet…
What’s very strange is editing the settings in AMIBCP for the same slot IOU0, doesn’t appear to work. The edited CAP file appears to have no changes compared to stock. Even though in AMIBCP it shows “Auto” has been changed to x4x4x4x4 for both Failsafe and Optimal fields.
This is further verified by extracting the body section with UEFITool of stock vs modded BIOS and diff in HxD, both blocks are identical. Curious what’s missing?
Hi @chinesestunna !
WOW!
That’s a really good news!
I couldn’t understand why the bios mod didn’t work for me while it worked for others. So I did not try the EFI Shell mod yet.
But thanks for the update I will try it and get back to you!
Can i ask one question?
What type is your quad ssd expansion card? And witch slots are populated?
Thanks buddy!
Thank you 
I’m glad I got this working so far and will look into the BIOS mod more closely as RU shows it’s not a board limitation and proof of concept.
I’m using this card: Pcie 4.0 X16 to M.2 M-key NVMEx4SSD RAID Expansion Card Adapter 4 x 32Gbps | eBay with 4x Samsung PCIe 4.0 (running at 3.0 of course on X99) 512GB NVME drives
How can I change the BIOS to make pciex16 work in x4x4x4x4 mode?
Hi folks!
I finally get this thing to work!
With this bios:
As it turns out the BIOS was good from the start.
Bifurcation was working by default.
The reason it wouldn’t work for me was because I had an M.2 card in the M.2 slot all along.
When I was browsing the motherboard description I noticed that even with a 40 lane cpu the PCI-E 3 slot can’t work in 16x mode. (If the onboard m.2 slot is occupied)
So I removed the ssd from the motherboard M.2 slot and put it into the HYPER V2 card, put the Hyper V2 card to the PCI-E slot and voila!
The system saw all 4 M.2 SSDs at once!
And the resizable bar still work as it should.
So, important notification for those who want to use this bios with 4x M.2 pci-e card:
The bifurcation only work in the PCI-E 3 slot, and with empty onboard M.2 slot.
And no further bios settings needed.
Thank you for the support all of you guys!
I have Asus X99 Deluxe II, 6950x, Asus Hyper M.2 x16 card with 4 different ssd (one system bootable)
Thanks so much everyone for the information here!
@superyin really appreciate your guide to modding the BIOS. The copy of the BIOS you uploaded back in 2023 is no longer available from the link. Can you reupload that please?
If anyone else has a copy of the modded BIOS that would be great too, for the ASROCK Rack D1541 board. Thank you!!