PCIE Bifurcation

chithanh

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Oct 18, 2010
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x0 means 0 PCIe lanes connected to the second slot. This is because the splitter will route lanes 0-7 to the first slot, and 8-15 to the second slot. But in a mechanical x16 / electrical x8 slot, only lanes 0-7 are connected.

To achieve what the previous poster wants, an x8 to dual x4 splitter is necessary.
 

Kabachi

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Feb 16, 2021
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2)no, one will work at x8 and the other one will get x0
So, if my goal is to get 8 PCIE cards working off a single motherboard, instead of trying to use every available slot and then splitting the last one one or two, I should instead only use slot combination that motherboard can provide with 16 lanes per slot and then use two of your x4x4x4x4 splitters? I don't see any x8 to dual x4 splitters with power connectors. This approach actually widens the motherboard selection quite a bit.

Or, make sure the splitter is in the slot that stays 16x when all slots are used.
 

Kabachi

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I do have an x4x4 card. https://peine-braun.net/shop/index.php?route=product/category&path=65_67
An x4x4x4x4 in the first slot would still be preferable I guess.
Your BIOS/CPU must be capable of supporting this though. Need to verify that first!
Damn, how did I miss your store link. I see you even have PLX splitters there, I wonder how those would show up in VFIO grouping for passthrough.

Those PLX splitters, let's say I am crazy and want to connect multiple PCIE cards to Intel Nuc that has an M.2 slot internally. I probably can buy an M.2 to PCIE x4 adapter (i.e. EXPLOMOS M.2 Key M NGFF to PCI-E 4X Adapter Card) + your PLX splitter and do it? Would it work with x4 PCIE? What about a similar stunt but with external thunderbold eGPU that also provides 4 lanes according to GPU-Z.
 
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Kabachi

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How difficult would it be to make something like this but in M.2 format (x4 -> x4x4 or x4->x4x4x4x4 for instance)?

Physical placement of all necessary components and the temperature of the PLX chip.
Need a smaller device, with less power consumption. (less power rails as well!)
Would the temperature and size be the only problem here? I am seriously tempted to try connecting your bigger PLX board to an M.2 slot via an ADT M.2->PCI x4 cable unless you can tell it is not going to work on just 4 lanes right away.
 

maeslin

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Apr 24, 2020
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C_Payne, I received the x8/m.2/m.2 riser and put it through its paces. It works beautifully!

20210218_214413.jpg

20210218_214429.jpg


Full passthrough for pcie x8 and a pair of m.2s in a low profile footprint. It's a work of art.
 

Neapolitan6th

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C_Payne, I received the x8/m.2/m.2 riser and put it through its paces. It works beautifully!

View attachment 330910
View attachment 330911

Full passthrough for pcie x8 and a pair of m.2s in a low profile footprint. It's a work of art.
Curious how this would ideally be installed? Love the product of course, super neat stuff. This is the one designed for the NCASE I believe. Any pics of the install by chance?
 

maeslin

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Curious how this would ideally be installed? Love the product of course, super neat stuff. This is the one designed for the NCASE I believe. Any pics of the install by chance?

It's actually designed for the U-NAS NSC-800, but should work in any other situation where you want to run a low-profile x8 card and still use the rest of the lanes. It's a tiny NAS case that fits a mini-itx motherboard and 8x 3.5" drives.


The bifurcating riser is connected to the motherboard, and a short length of flex riser goes from that riser to a LSI9211-8i SAS2 card installed in an offset position. Across the top is a Mellanox Connectx-3 in a 3d-printed retainer bracket, connected to the motherboard's m.2 slot through a m.2 to pcie x4 adapter.

In total, in that small case, I have the motherboard/cpu/memory, 8x 4TB SAS2 drives, 2x 2.5" SSDs, 2x nvme drives, a SAS2 card, a Connectx-3 card and a pair of 120mm fans.

About as packed as it can get for a case that's 12"x10"x7" (~13.7 liters)
 

Neapolitan6th

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It's actually designed for the U-NAS NSC-800, but should work in any other situation where you want to run a low-profile x8 card and still use the rest of the lanes. It's a tiny NAS case that fits a mini-itx motherboard and 8x 3.5" drives.


The bifurcating riser is connected to the motherboard, and a short length of flex riser goes from that riser to a LSI9211-8i SAS2 card installed in an offset position. Across the top is a Mellanox Connectx-3 in a 3d-printed retainer bracket, connected to the motherboard's m.2 slot through a m.2 to pcie x4 adapter.

In total, in that small case, I have the motherboard/cpu/memory, 8x 4TB SAS2 drives, 2x 2.5" SSDs, 2x nvme drives, a SAS2 card, a Connectx-3 card and a pair of 120mm fans.

About as packed as it can get for a case that's 12"x10"x7" (~13.7 liters)
That's incredible. I've been wanting to do something similar and yours is certainly a great example to strive for. I was actually just made aware of that NAS case. Shame its not sold anymore by the looks of it. Might have to bite on some of the ebay listings I see of it even with their markup. For 8x 3.5 HDDs and as much functionality as you've been able to squeeze out of such a small case, it seems like a no brainer. Thanks for sharing!
 

maeslin

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Apr 24, 2020
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Shame its not sold anymore by the looks of it.

AFAIK it might just be out of stock? Could be worth contacting them to see if they are going to restock soon. The NSC-810 and 810A were released after I got it and might be a bit more convenient. The 810 takes a mini-ITX board and doesn't need a flex riser, while the 810A can handle micro ATX boards.
 

Mosquito

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Feb 9, 2020
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I had never heard of the U-NAS cases before, but they are pretty sweet. I like the 810A idea, and also maeslin, your build out is awesome!
 

maeslin

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Apr 24, 2020
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I had never heard of the U-NAS cases before, but they are pretty sweet. I like the 810A idea, and also maeslin, your build out is awesome!

Thanks! Here's pictures of the full build for reference:

One little word of advise with those cases; they tend to have some pretty sharp edges inside. Get some grommet edging ('grommet strip') if you get one of them, it'll save both cables and fingers.
You can see what I mean surrounding the holes where the power cables and SAS cables feed through in pictures 1, 15, 33, 35 and 37.
 
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