Niche' ROMED4ID-2T PCIE Ports usecase

Hardware Hub Motherboards
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Hello all together i hope i can get an insight in what iam doing wrong. [image]

I have an ROMED4ID-2T board and an Epyc CPU Rome in it, i have an 1U case and want my GPU to be seated in the “front” since my PCIE Slot7 (Pcie 16x Slot) is occupied by my Mellanox 100Gbe NIC i want to adapt 2 of those SlimSAS (PCIe 4.0 x8) Ports to one PCIe 16x Slot.

AFAIK the Slim Ports 5+6 are linked together by PCIE lanes Pcie G1 0-7, 8-16

so i bought good cables and two of those SlimSAS PCIe gen4 Device Adapter 2* 8i to x16 daughter boards.

so what works and what not, both do 1x8 Mode no problemo but not 16x Mode.

edit

16x
8x8x
4x4x4x4x

Its all there

edit

I tried to interchange the cables but no 16x, i tried every bifurcation mode in the Bios.

Maybe i have to change something else? Has anybody tried something similar.

regards Dom

https://de.aliexpress.com/item/1005005606630142.html?spm=a2g0o.order_list.order_list_main.22.1a045c5f1dVxdh&gatewayAdapt=glo2deu

24G Internal SlimSAS SFF-8654 to SFF-8654 8i cable, Straight to Left Exit, SAS 4.0, 1-m, 100ohm

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The outcome interests me as well.

Does the BIOS offer the option to set 16x mode for SlimSAS 5/6 or does it only offer 8x8 or 4x4x4x4?

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Yes

16x
8x8x
4x4x4x4x

Its all there :slight_smile:

Same goes for Port 1 and 2

And

2 and 3

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Hmm so if I understand the diagrams/description correctly the connection from SlIMSAS5 should go to the connector near the power plug (1st connector on board) and SLIMSAS6 should go to 2nd connector on board.

What happens? Is it still recognized as x8 or not recongnized at all?

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still 8x, i always do a full reboot and check with lspci -vvvn -s 45:00.0 | grep LnkSta

45:00.0 is my Nic ID

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c-payne card are only a cable extender for a pci slot. if you have a pci double slot or thicker, you plug a dongle and then you feed that card with 1 or 2 cable. no bifurcation stuff, it’s only a direct wire extender.

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I gues thats fine i refer to this bios Setting here

IMG_0341
IMG_03414284×5712 8.13 MB

and that diagram from the Manual

Screenshot 2024-01-31 174855
Screenshot 2024-01-31 1748551551×1039 188 KB

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Just wondering. DId you hear anything back from Asrock Rack support?

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Dear Sir,

Thank you for contacting ASRock Rack support.

Sorry but I do not have experience with this type of card. Even so the ports will remain at x8. Maybe one of the ports take precedence ?

Regards,

ASRockRack TSD

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Any luck with your build?

I saw that ASRock Rack uses this setup in their 1U2N2G-ROME/2T barebone server that has two of these motherboards in a 1RU chassis. They support a x16 pci slot from each board that is driven from the slimline SAS ports. One node uses SlimSAS 5+6 like you were trying and the other node uses SlimSAS 2+3. ServeTheHome has a really good youtube video with lots of closeups of how everything is wired up. There is a good view of their riser card with part number 1U4G_SL2P_L_RDV.

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my best bet is that the adapter they are using is a retimer and not a simple card like that from c-payne, igues i can get it to work with shorter cables but that defeats my purpose.

but good to see that Asrock made it work and the support shamed themselfe :smiley:

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I’m going to try with a quite dumb question. Did you try to swap connections on your daughter-card? I mean, is it possible that you mixed up 0-7 and 8-15 parts on it?

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That question is not dumb :slight_smile:

And yes you can believe me that i tryed ALL combinations.

I did not trust myselfe, Asrocks Manual and both manifufactors of those boards. :smiley:

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Thanks for the reply, sir. I will watch the topic, since I will be facing the exact same scenario myself in a couple weeks. ITX Epyc and 4x 24gig VRAM is just… something too attractive, so I’ve made my orders. I will also come back if I happen to know a solution, for sure.

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for AI the 8x per Port is fine AFAIK… its my next move with this board, when the RTX 5000 series comes out i can sell my RTX A4500 and buy some P40 from that for LLM Home usage.

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I thought that P40, while being similar in VRAM size to 3090, still lacks the tensor cores, so FP32/16 will take place on the CUDA cores - which is not bad, but still loses a bit in ttft and t/s values.

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Yea i mean, iam not rich and it will be for homeusage so it will work just fine enough i gues :smiley:

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@leftoverscrew, is the video I posted the video you are talking about?

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Yes that’s it

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