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


10 posts in this topic Last Reply

Recommended Posts

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

 

 

Link to post
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

Link to post
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.

Link to post
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.

Link to post
  • 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.

 

 

Link to post
On 6/10/2021 at 10:27 AM, JorgeB said:

Unraid is not optimized for those speeds

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

Link to post
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.

Link to post
  • 1 month later...
On 6/9/2021 at 1:31 AM, mgutt said:

I found one B550 board with 4x x4 Bifurcation Support:

https://dlcdnets.asus.com/pub/ASUS/mb/SocketAM4/ROG_STRIX_B550-E_GAMING/E16546_ROG_STRIX_B550-E_GAMING_UM_WEB.pdf

 

image.thumb.png.484c41b6b59a71d20ff541eb52d333a5.png

 

image.png.145ae6f3b6619a09775a0b1fea9e2e95.png

 

image.png.7997ab1a16f5700c272fe2c76b4cc9be.png

 

 

By that this board should support:

- 7x NVMe: All x4 (PCIe to M.2 adapter in slot PCIE16_3)

 

 

Here's another one.  ASRock Rack X470D4U Hope it helps!

Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.