Z840 PCiE Bifurcation support

[ZColin]

Recently purchased a Z840 and I'm trying to install 2x Samsung 960GB M.2 (M key) NVMe SSD's.  I bought a 10GTek NV95N8 dual NVMe M.2 M key PCiE card.  I upgraded the BiOS to 2.54 and I see the bifurcation option in the slot configuration. I set the bifurcation option to x8x8 (slot 6) and have the PCi card installed on slot 6.  

Windows is only seeing 1 out of 2 drives. Tried moving it to other PCiE slots only for CPU 0 since, I only have one proc. but to no avail. I know for a fact that the other NVME works because, I tested by removing one NVME on the card and booting it up for both. Any help would be appreciated

[DGroves · Accepted solution]

from the listed card specs posted online: this cheap m.2 card does Not support bifurcation

• Support 2x M.2 NVMe SSDs for 2230,2242,2260,2280 and 22110mm
• PCIe 3.0, X8
• SSD not include
• Not support bifurcation

this card uses bifurcation

https://www.asus.com/us/Motherboard-Accessories/HYPER-M-2-X16-CARD-V2/

this card will work in z820 (and z840) systems as it does not use bifurcation, but will also work on most systems that have bifurcation support

https://www.amazon.com/CREST-SI-PEX40129-Ports-Bifurcation-Controller/dp/B07HYZY7P2

[Brian1965]

M.2. drives only require 4x PCIe lanes, you need to set slot 6 bifurcation mode to x4x4x4x4 to see both drives, not x8x8. i.e. the adapter card does not combine the drive outputs into a single x8 data stream, rather they are treated as 2 x4 data streams. All RAID operations are managed by either the motherboard BIOS (hardware RAID), or the OS (software RAID).

[ZColin]

Thank you Brian! You are a genius. That worked! I see both NVME drives now after changing the mode to 4x4x4x4x