@SuperDicq >For example lots of expansion cards simply require PCIe 3.0 minimum to function at all.
Those devices are not compliant with the PCIe specification - compliant cards will operate even in a PCIe 1.0 port, albeit at a reduced speed.

>The AMD boards run exclusively ECC ram sticks and they can be really damn picky when it comes to RAM sticks.
Not really? I found that you just need to get quality double-sided (not single-sided) sticks from Hynix or Micron and avoid Kingston ones (fairly cheap in ex-server DDR3 ECC RAM bundles).

Even then, I managed to get mixed Hynix/Kingston to work in a non-standard layout too.

A GNUboot developer is fixing up the RAMinit, so eventually RAM support will be much improved.

>And yes the AMD boards are capped at 128 GB.
According to the vikings page you posted, 192 GB can be reached with most quality DIMMs and 256GB can be reached with a specific DIMM models.