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X399 Motherboards with Bifurcation support?



So in all my googling these past couple hours I cannot seem to find out which X399 motherboards support PCIe Bifurcation, can anybody recommend?

Also I’m not sure which has decent IOMMU groups for passing stuff through to VMs and whatnot as I’m likely going to start dabbling in that in the near future.

Boards I have to choose from at the moment are:

  • MSI X399 Carbon
  • Asrock X399 Taichi
  • Gigabyte X399 Gaming 7

Would love any help in choosing which motherboard I should go with or if another would suit me better.


Go ahead and vote if you want too! (fancy feature I haven’t tried yet:P)

  • MSI X399 Carbon
  • Asrock X399 Taichi
  • Gigabyte X399 Gaming 7
  • Other X399

0 voters


Asrock X370 and X470 ITX boards support Bifurcation. Not sure if that carrys through to the rest of their lineup.



From a bit more searching I found a post that claims it works on the Asrock boards so I’m definitely leaning towards one of those


Bit late to the party but I’d just like to mention that the Aorus Xtreme also supports it, if that’s any use.


AsRock x399 Taichi and Professional Gaming both support Bifurcation on their 3rd PCIe x16 slot (last time I checked, may be allowed on top slot as well now)


Last time I was in BIOS (recently updated to v3.30), all full length slots on the X399 Taichi support bifurcation.
Previous BIOS (v2.00), from memory, only supported the 3rd slot.


I have the ASRock X399 Taichi and it has mostly great IOMMU groups. I dislike the following traits, but none of them is a dealbreaker to me:

  • Both onboard NICs are in the same IOMMU group (with a bunch of other stuff). I believe this is due to the X399 chipset, though.
  • The temperature source setting for fan control in the BIOS is not optimal. Only the very volatile Tdie or the slow / imprecise socket temperatures can be used. There really should be a time-averaged Tdie source.
  • More of a GPU problem than a motherboard problem: I have two 2-slot GPUs in the x16 slots, which only leaves me with the PCIe x1 slot. But this is attached to die 0, I would need it on die 1. This means that I will need a 1-slot GPU for the host.

I use 4x 8GB 3200 CL14 RAM and don’t have any stability issues whatsoever. I have heard of others who had to use lower clocks on motherboards of other manufacturers because they ran into issues.

Can’t say anything in regards to bifurcation.

Edit: Just saw that this thread is over a month old, whoops. Sorry about that, but maybe it will help someone else.


No worries, The info is helpful :slight_smile:

I ended up getting the X399 Taichi board myself and when I checked the UEFI all slots supported PCIe bifurcation but only in the x4 variety (so an x16 slot can only be an x16 or an x4/x4/x4/x4)

Was hoping for and x8/x8 option :confused:

I’ve heard of some boards BIOS’s being modified to support it, anyone have any info in that regard?

Thanks for all the replies BTW!


The Asus Zenith extreme x399 can support bifurcation accross all pcie and be x16→x8x8/x4x4x4x4/2x2x… Or the combinations of them to make x16 from reading their product page and bios reviews


That is great to know, thanks for sharing!

if I don’t figure out a way to work around the x4/x4/x4/x4 limitation then I might pick one of those up :+1:


Hi, I’ve been looking for the bifurcation settings on a Gigabyte board…can you tell me where they are? I have an Aorus X399 Gaming (not Xtreme), but hopefully, they are in same place…Thanks!