DELL T7920 nvme u.2/m.2/bifurcation problem

[REGEN]

Hello,

I have DELL T7920 workstation and I have a big question about bifurcation board and pci-e > m.2 adapters for this dell 7920.
M.2 adapters or pci-e ssd's works only in 2 slots (see picture), on 7820 situation is the same. Also, bifurcation is not working at all, I managed to see (recognize in windows and bios) 1st (one) ssd from bifurcation board on the same 2 "yellow' slots only (see pic) only. I tested bifurcation with 4 ssd's on dell t7810 and it works flawlessly plug&play...

Maybe there is some options in bios for this?

Also I attached my intel 750 pci-e ssd via cable to the back of the motherboard and dell T7920 stated no ssd found... I tryed to see it in windows install manager and bios, I tryed to connect it to each (4 total) u.2 minisas slost on the back (see picture) and nothing... Can you please help me with it?

 

[mrpasc]

This automated bifurcation on T7820 / T7920 is kind of finicky. Had the best results with VMD disabled and needed to clear CMOS every time I added a new card. Then it worked (it powers on and off several times, after that bifurb was active).
Never got the SFF-8436 working with direct attached U.2, only with the optional U.2 backplane. Guess it is some proprietary wireing…

 

[REGEN]

This automated bifurcation on T7820 / T7920 is kind of finicky. Had the best results with VMD disabled and needed to clear CMOS every time I added a new card. Then it worked (it powers on and off several times, after that bifurb was active).
Never got the SFF-8436 working with direct attached U.2, only with the optional U.2 backplane. Guess it is some proprietary wireing…

It worked in specific slot?
It was genuine dell board or something like this?

https://forums.servethehome.com/index.php?attachments/images-jpg.35611/

Thanks

 

[mrpasc]

Yes, it worked in the x16 slots and with ASUS x16 to 4x M.2 adapters. But not more than 2 of the x16 slots became bifurcated at a time. Tried a third one for additional 4 M.2 and this ended with only the first M.2 of the third one was usable.

 

[hkdio]

Same issue.

Using genuine dell 06N9RH.

If only 1x NVME, T7920 can detect that SSD.
But if 4 x NVME, All SSDs can't detect

x16 slot tested and not success.

 

[CyklonDX]

PCIe Bus Allocation in Dell Precision 5820 | 7820 | 7920 Tower | Dell US

It could be something that it doesn't like your adapter card, asus x16 to 4x m.2 adapter is documented to work just fine.