pci-e 3.0 4x4 riser?

[Lapsio]

I have no idea whatsoever in which category to post such question but I'll give it a try here given why I'm looking for such thing.

 

I'm looking for some pci-e 3.0 pci-e riser x16 -> 4x4. It'd be nice if it was powered to avoid motherboard overload but It's not required. The only thing suitable for PC I found for now is Asus HYPER M.2 x16 card using additionally 4x M.2 -> pcie x4 adapters. Is there maybe something more... adequate? I was looking at Supermicro server risers but they're either 2x8 or something like 2x4+8 and those modes don't seem to be supported by ASRock X399 motherboards or pci-e 2.0 capable. I'm in need for more pci-e slots in virtualization server based on Threadripper and x4 speed seems to be enough for most quad gigabit network cards, gpus, SATA controllers and all other kinds of stuff I'd need.

 

Also does anyone know how such risers behave in terms of IOMMU grouping? I'd like to connect lets say 2-3 GPUs and network card to it and then pass them various to headless KVM VMs so they should land in separate IOMMU groups. ASRock motherboards support SR-IOV so I can just grab single AMD S7150 for all Windows VMs but it unfortunately doesn't support Linux guests so I need also bunch of physical junk GPUs for Linux VMs. I know NVidia Tesla M60 supports Linux guests but NVidia charges insane 350$ per Linux VM annually for GRID drivers (what the fuck NVidia) so the only viable solution I see is to just stack dozen of cheap junk GPUs via riser and pass them through.

[Snipergod87]

It can work if your motherboard supports PCI-Express Bifurcation, which allows splitting one 16x slot into multi lesser slots.

This feature is typically only found on server boards, but may be present on HEDT chipsets.

[Lapsio]

2 hours ago, Snipergod87 said:

It can work if your motherboard supports PCI-Express Bifurcation, which allows splitting one 16x slot into multi lesser slots.

This feature is typically only found on server boards, but may be present on HEDT chipsets.

It is supported on ASUS x399 and ASRock x399 motherboards. I even asked ASRock tech support to add 2x8 config because they used to support only 4x4. So support is here. Now I need to find actual riser in some shop. I can't seem to find anything suitable.

[Mbarton]

On 5/20/2018 at 1:43 AM, Lapsio said:

It is supported on ASUS x399 and ASRock x399 motherboards. I even asked ASRock tech support to add 2x8 config because they used to support only 4x4. So support is here. Now I need to find actual riser in some shop. I can't seem to find anything suitable.

Ebay is your friend when looking for odd parts.