[vfio-users] z370 iommu groupings

[Taiidan at gmx.com]

No matter what you get I would advise against getting a non-server board 
where you won't be getting support for what they consider to be a server 
feature, someone with a "gamer" board who says IOMMU works may have a 
different revision than what is currently being sold - getting it 
working is always a fluke at best,

What are your goals for this build? What programs will you be running?


Honestly 4 dual slot cards on the same board is a really tall order and 
wouldn't leave you with space for peripheral cards if you want real USB 
controllers instead of emulated controllers.
You might consider buying a GPU type PCI-e expansion system such as the 
ones from cyclone microsystems which are dual slot spaced and would 
leave you with enough room for other cards.
http://www.cyclone.com/products/expansion_systems/600-2711.php

If you don't need x86-64 and if you really need to max out the bus on 
your video cards I would consider a POWER9 machine such as the TALOS 2, 
the company who makes it has released firmware for other boards that has 
excellent IOMMU groups and they actually reply to my technical support 
emails.
https://raptorcs.com/

With two CPU present you would have 4 PCI-e 4.0 x16 slots with one of 
those x8 electrical although they aren't dual slot spaced so you would 
need either an expansion system or single slot cards such as the Radeon 
Pro WX series.
POWER9 is about to be released and it has a variety of advantages such 
as PCI-e 4.0 and 4 SMT threads per core for sforza.