PCIE BIFURCATION INTEL XEON 2699V3

[unresponsive-penguin2220]

Hello everyone,

I have an intel S2600WTT server board with 2x XEON E5-2699 v3, 1x Intel A2UL8RISER2 Riser Card, and two sata hdd's.

Here is my issue, I just recently purchased an ASUS Hyper M.2 x16 PCIe 3.0 x4 Expansion Card and have installed  1X SABRENT 1TB Rocket NVMe 4.0 Gen4 PCIe M.2 and 1x SABRENT 500GB Rocket Nvme PCIe 4.0 M.2.  The ASUS Hyper is installed into the 1st slot (top) on the riser card in Slot 1 of the server board PCIE connector.

 

The riser card has all three slots at x8 written next to each slot (with the top two using a PCIE x16 plugin, and the third is a x8 plugin). I checked ASUS's website on the quad m.2 card to see if it can be bifurcated and it looks like i can (https://www.asus.com/support/FAQ/1037507/). 

 

In the BIOS, there is a selection for PCIE bifurcation. In there, the bifurcation selections only shows up in the other PCIE server board slots that is not populated with the riser card (very frustrating) (meaning if server board slot 1 is populated, slot 2 and 3 bifurcation setting will show up.)

Selections are 4x4x4x4 or 8x8 for slot 1 and 2, and 4x4 or 8 for slot 3.

 

Of note, the ASUS card is recognized by the system and unraid, but only the 1st of the four M.2 slots is read.

 

Do I need to get a dual or quad M.2 expansion card that is bifurcation only like this one (https://www.newegg.com/p/17Z-0061-000B2?Item=9SIARE9JVF1975) or am I screwed? or do I need to get an expansion card that is x8 and not x16? Thank you!

 

Also, I saw the other forum with similar issues but I want to see if anyone can help from my setup. 

[JorgeB]

I can confirm the Asus adapter will only detect the 4 devices if the board can bifurcate the slot to x4/x4/x4/x4, and that's always controlled by the board BIOS, another adapter that requires bifurcation wiil have the same result, there are adapters that don't, they have a PLX chip, but they are usually considerably more expensive.

[X09C]

So would i need to plug in the asus pcie directly into the slot of the motherboard?  Or can i continue to use the riser card that I bought and plug the asus pcie into the riser? or does the riser need to have bifurcation built in (if this if what you are saying?)

 

Something like this EBAY RISER CARD

Edited December 8, 2023 by X09C

[X09C]

So just to clarify, the first two slots are riser slots and the 3rd is x16 slot.  I plugged the asus card directly into the third slot, powered it on, and now the drives are missing.  This is wierd. 

[JorgeB]

9 hours ago, X09C said:

So would i need to plug in the asus pcie directly into the slot of the motherboard? 

Correct, as long as bifurcation can be enabled in the BIOS for that slot.

[X09C]

you have been most helpful and I would love to pick your brain some more.  

If plugging the asus card into my x16 slot on the server board works, then why doesnt the same function occur with the riser card within the 1st two slots of the server board?  

Attached is a page from the TPS showing x8 elec and x16 mech for the 3 slot riser card and attached is a bios screen shot.  the risercard is populated in riser slot 1, which makes it not show up in the bios.  This happens when i switch it to riser slot two, then 1 and 3 show up.  

[JorgeB]

2 hours ago, X09C said:

Attached is a page from the TPS showing x8 elec and x16 mech

If the slot is x8 elec it won't work with all 4 devices, needs to be x16 elec.

[X09C]

Ok, so I think I am actually understanding this stuff now.  Basically, if the card was a x8 interface (electrical) with a x16 slot (mechanical) then it would work in the top two slots.

 

[X09C]

I give up on this stuff.  I have tried in all three slots on the riser card with a new startech DUAL-M2-PCIE-CARD-B that is pcie 4.0 x8 as we talked about.  It works but only the first slot is recognized of the two.  So I took out the second m.2 stick from the startech card and placed it in a pcie 3.0 x1 card that I had laying around and placed that in the 3rd slot of the riser with the startech in the 1st slot.  

That works and both m.2's show up now in unraid.  I do not understand what is going on. 

 

If we are going way beyond your capabilities, please let me know.  I do need to try reddit again. 

Also do my ssd's need to be pcie 3.0? because they are 4.0.  Also i changed all three slot bifurcation settings to default.

Edited December 12, 2023 by X09C

[JorgeB]

3 hours ago, X09C said:

I have tried in all three slots on the riser card with a new startech DUAL-M2-PCIE-CARD-B that is pcie 4.0 x8 as we talked about.  It works but only the first slot is recognized of the two. 

That suggests PCIe bifurcation is not supported or enabled for that slot.

[X09C]

So update, on my other unraid server - it is an asus x99 deluxe ii - i am running an LSI 9201-8i.  So i took that and plugged it into my intel server within slot 2 of my riser card and attached to velociraptor HDDs into it. viola they both show up.  I am assuming it is because this card has a PEX chip, which i think is under the heat sink.