AsRock X570D4U - PCIe bifurcation issues

[dave_555]

Hi everyone.
I'm building a small server:
- AsRock X570D4U
- Ryzen 5900X
- 2 x 32 Gb Kingston KSM32ED8/32ME (QVL)
- Supermicro AOC-SLG4-2E4T connected to 2 x Samsung PM9A3 1.92 Gb through Supermicro CBL-SAST-0953 cable

I though there would be no problems but I was wrong...

There's no way to make the AOC-SLG4-2E4T work. No bifurcation option has any effect, so I assumed there was a compatibility issue.

Yesterday I received two of this: U.2 PCIe 4.0 Adpater for 2.5 inch U.2 SSD (SFF-8639)
I've installed one in the PCIe slot 6 and the other in the slot 4. Only this latter one is seen, I've tried all bifurcation option also.

Maybe the PCIe slot 6 is damaged?
Don't have any card to install in it.

 

[llowrey]

It does sound like slot 6 is damaged if you have success with slot 4. At no point is slot 6 without lanes allocated.

I have two of these boards and bifurcate on both. On one board I have an x8 NIC in slot 6 and a x8 HBA in slot 4 (bifurcated via x8x8). The other board has an x8 NIC in slot6 and a dual u.2 breakout in the other (bifurcated via x8x4x4... or x4x4x8... I can never remember which).

I'm guessing the AOC-SLG4-2E4T would need to be in slot 6 with x4x4x4x4 or in slot 4 with x8x4x4.

Do you have anything else you can put in slot 6 to test the slot?

 

[dave_555]

I've done several tests:
- AOC-SLG4-2E4T in slot 6 bifurcated in every single way -> zero success
- AOC-SLG4-2E4T in slot 4 bifurcated in every single way -> zero success
- U.2 adapter in slot 6 -> zero success
- U.2 adapter in slot 4 -> works
- U.2 adapter in slot 6 + U.2 adapter in slot 4 -> works only slot 4

Maybe the AOC-SLG4-2E4T is not compatible or the slot 6 is damaged or bifurcation doesn't work (maybe both the two last).

I don't have other cards right now, maybe tomorrow a NIC or a graphics...

 

[dave_555]

I have two of these boards and bifurcate on both. On one board I have an x8 NIC in slot 6 and a x8 HBA in slot 4 (bifurcated via x8x8). The other board has an x8 NIC in slot6 and a dual u.2 breakout in the other (bifurcated via x8x4x4... or x4x4x8... I can never remember which).

Have you changed PCIe slot 6 mode only in BIOS settings to make it works or other parameters also?

 

[llowrey]

Have you changed PCIe slot 6 mode only in BIOS settings to make it works or other parameters also?

I do not recall making any other changes to the BIOS wrt to any slots. AFAIR I just set the bifurcation mode.

Note that the AOC-SLG4-2E4T manual says to do the following in addition to setting bifurcation to x4x4x4x4:

8. Enter the IIO DFX Configuration menu.
9. Select CPU1 Configuration.
10. Select the appropriate port option.
11. Under Preset Settings, select DN Tx Preset and modify it to P7

Seems that has something to do with the configuration of the retimer that's on the board. Not sure how to translate that to this board.

Just to be clear, slot 6 is the one closest to the CPU. That will always have at least 4 lanes allocated to it so a card should always work in that slot unless it is unable to negotiate down to x4.

 

[dave_555]

Note that the AOC-SLG4-2E4T manual says to do the following in addition to setting bifurcation to x4x4x4x4:

8. Enter the IIO DFX Configuration menu.
9. Select CPU1 Configuration.
10. Select the appropriate port option.
11. Under Preset Settings, select DN Tx Preset and modify it to P7

Seems that has something to do with the configuration of the retimer that's on the board. Not sure how to translate that to this board.

Yes, I know. AsRock support already reply me that they don't know about Supermicro products...

Just to be clear, slot 6 is the one closest to the CPU. That will always have at least 4 lanes allocated to it so a card should always work in that slot unless it is unable to negotiate down to x4.

The adapter I'm using is a PCIe 4.0 4x to U.2, one in slot 6 and the other in slot 4.
I tried to switch them but only the one in slot 4 works.

I'll text AsRock

 

[dave_555]

UPDATE

I've installed a 16x graphic card and it works, so PCIe slot 6 is not damaged at all.
Added the PCIe 4.0 4x to U.2 adapter in slot 4 and the SSD drive is correctly seen together with the graphic card (so bifurcation/mux works).

At this point I can say that the motherboard and the adapter are both ok, but there is a compatibility issue for sure.
It is very strange because the same adapter works in slot 4 but not in slot 6...

Anyone has tried/knows a PCIe gen 4.0 (4x or even 8x with bifurcation) to U.2 SFF-8639 adapter compatible with X570D4U?

I've found these Delock, but can't understand the difference:
Delock Products 90081 Delock PCI Express x4 Card to 1 x internal U.2 NVMe SFF-8639
Delock Products 89469 Delock PCI Express x4 Card > 1 x internal U.2 NVMe SFF-8639
and this one from Startech:
Adapter, U.2 to PCIe - 2.5' U.2 NVMe SSD - Drive Adapters and Drive Converters

 

[dave_555]

UPDATE

Startech adapters work like a charm. Both are correctly seen out of the box.

Not my ideal solution as all PCIe slots are occupied for 8 lines total, but I don’t need more right now.