Which B550 AM4/1151/1200 supports 4x x4 Bifurcation (x4x4x4x4)?


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I only find server boards with 2011-3 sockets or high power boards with X570 AM4 supporting x4x4x4x4 Bifurcation. I mean yes, both have more Lanes, but only für switching an x16 PCIe slot to x4x4x4x4 this is not relevant.

 

Most B550 AM4/1151/1200 boards already switch between two (mechanical) x16 Slots, so they become x8 + x8 on usage. And the Gigabyte W480M even allows x4x4 + x8, but I can't find one, where you can have x4x4 + x4x4 or x4x4x4x4 + none.

 

It would be so nice having much more M.2s without adding an expensive Quad card with controller (30 vs 600 Euro).

 

Did anyone stumble across a B550 AM4/1151/1200 board with x4x4 + x4x4 or x4x4x4x4 support?

 

EDIT: I found this in the specification of the Asus Prime Z590-P. Does it mean it's a general limitation of Intel Consumer CPUs?

 

Quote

 

- Intel® 11th Gen processors support PCIe 4.0 x16 or x8/x8 or x8/x4/x4 modes

- Intel® 10th Gen processors support PCIe 3.0 x16 or x8/x8 or x8/x4/x4 modes

 

 

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On 2/4/2021 at 10:01 AM, mgutt said:

I only find server boards with 2011-3 sockets or high power boards with X570 AM4 supporting x4x4x4x4 Bifurcation. I mean yes, both have more Lanes, but only für switching an x16 PCIe slot to x4x4x4x4 this is not relevant.

 

Most B550 AM4/1151/1200 boards already switch between two (mechanical) x16 Slots, so they become x8 + x8 on usage. And the Gigabyte W480M even allows x4x4 + x8, but I can't find one, where you can have x4x4 + x4x4 or x4x4x4x4 + none.

 

It would be so nice having much more M.2s without adding an expensive Quad card with controller (30 vs 600 Euro).

 

Did anyone stumble across a B550 AM4/1151/1200 board with x4x4 + x4x4 or x4x4x4x4 support?

 

EDIT: I found this in the specification of the Asus Prime Z590-P. Does it mean it's a general limitation of Intel Consumer CPUs?

 

 

 

@Intel: I think its by design - Intel CPUs can only handle x16 or x8x8 - The manufacturer determines how the lanes are interconnected by the chipset

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7 hours ago, JorgeB said:

Most can also handle 1x8+2x4, that's what I have on one of my servers with a Skylake CPU.

 

As far as i know, the 3rd PCIe-Slot is always connected to the chipset (on Mainstream-Platforms) - but maybe a Xeon can handle this different.

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10 hours ago, Zonediver said:

3rd PCIe-Slot

Usually it's not a 3rd slot, it allows to bifurcate a x8 CPU slot as two x4 slots, so for example I have an HBA in one slot and 2 NVMe devices in another, and most CPUs support it, no need for a Xeon.

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  • 4 months later...
23 hours ago, mgutt said:

This should allow a ~2000 MB/s array.

Possibly, but doubt it, Unraid is not optimized for those speeds, as an example see a read check with 5 NVMe devices (no parity):

 

image.png.fc258830aea2ed232c2488603bbc26f9.png

 

Single NVMe device was already only about 2.4GB/s, but speed starts decreasing as you add even more.

 

 

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1 hour ago, mgutt said:

As you didn't use a parity, I think this was a different bottleneck. Maybe two M.2 NVMe through Intel DMI?

No, they are all on CPU slots, it's a Xeon e5 v3/v4 board, with 40 PCIe CPU lanes, well 36 usable since 4 go to the onboard NICs.

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