Thanks, thats what I expected, since if each one of the 4 needs full bandwidth, even with Quad channel, each one „only“ has single channel speed available to them.
Since I want to use the thing as a home server while there is no LAN party going and i want to prioritize stability in general, I am considering ECC RAM, which wont get faster then DDR 2666 CL 19 (= 14.3 ns latency) .
Will that be a big hit vs going for normal DDR 3000 CL 15-16 (10 - 10.7 ns latency)?
Just want to throw in some advice that PLX chips are a big maybe in terms of IOMMU grouping. PLX chips could ruin grouping in some cases, while in other cases do the exact intended purpose… There’s not enough documentation on PLX chips and IOMMU.
You want a board with slot bifurcation. ASrock has it on some of their boards, so that might be worth looking into.
Well, TR has 64 lines natively, so no need for PLX chips, correct?
I got the ASUS Prime x399-A for $200€.
However, im interested in how to determine if a board supports slot bifurcation.
According to manual this board supports bifurcation:
PCIEX16_1 Bandwidth
[X16 Mode]
The PCIe x16_1 slot runs at x16 mode.
[PCIe RAID Mode]
The four PCIe x16 slots all run at x4 mode, which allows you to create a
RAID array of up to 4 PCIe devices
...
technically true.
You lose 4 lanes to the chipset, an additional 4 for each M.2 slot (2x on the X399-a) and up to 4 for each U.2 port.
So, you’re left with 48 PCIe lanes on the X399-a, if they’re all going directly into the CPU, and why wouldn’t they be?
With 48 lanes, that leaves you with a mere 3 slots at 16x.
So, yes, even Threadripper needs PLX chips.
The manual says the following
16 + 8 + 16 + 8 = 48
So that could be released without PLX chips, but did they?
Or does 16/8/16/8 only refer to Multi-GPU, and e.g. the 2nd slot is indeed capable
of a 16x connection?
Are there more pcie slots on the board?
If so, they’re either going through the chipset or connected via PLX.
This indicator is very likely referring to the wiring of the slot. It’s probably physically 16x, but electrically 8x.
The BOM (Bill of Materials) is in!
I ordered:
https://geizhals.de/?cat=WL-1349090
1x 1920x
4x DDR4 ECC 2666 CL19 16 GiB
1x USB Controller Card
2x 20 cm PCIe x16 riser card
3x USB 3.0 Hub
1x CPU Cooler
Will attempt the build on Saturday, if the Motherboard arrives in time.
Wish me luck! 
PS:
I have mice, keyboards, storage, monitors, GPUs, and a MaxTytan 800 W here. Anything I missed?
EDIT: added PSU I forgot to mention
You need at least an 800w PSU and proper case cooling. 4 GPUs and a big threadripper swirl around a bit of heat when all pegging 100% utilization.
Forget to mention that i will use a Enermax MaxTytan 800 W for the moment, thanks for the hint!
https://geizhals.de/enermax-maxtytan-800w-atx-2-4-emt800ewt-a1694232.html?hloc=at&hloc=de
Hopefully the RX 560s you have only need one 6+2 power cable. It seems that PSU has 6 PCI-E power slots but the cables only have one 6+2 connector each, instead of splitting into two.
Also I would suggest having a large NVME drive for hosting the OS vdisk for each VM, running off spinning drives is hair graying slow. But you should be able to share steam library so each game doesn’t take up 4x the space. I’m using the 1TB evo plus which has been quick and doesn’t heat up too much with my games on storage pool.
Once you do get all put together a couple more tips I’ve come across to ease the pain.
AMD cards don’t play well with Adrenaline drivers on i440fx. q35 with qemu 4.0+ has been working very well.
With Nvidia the smoothest process I’ve found is q35 or i440fx with no hyperV, install OS without passing GPU yet, then pass GPU, start NVIDIA driver install and don’t continue after it extracts the drivers. Manually install driver in device manager, then continue the Nvidia drivers installation. Others haven’t had issues doing other processes but I got error 43 if I did it any other way with my 1080 ti.
How can you do that? Is this a steam feature?
Not a Steam feature per se. You just create a Steam Library share drive. In each VM you have to map the share as admin. Then in steam you set the library/download location to the share drive. I found this reddit post that explains better https://www.reddit.com/r/unRAID/comments/591y4r/keeping_your_steam_library_on_a_network_drive/
I had this working fine on my last server, haven’t gotten around to it with my new build. Might give it a go this weekend to make sure it all works the same. I also had a windows update cache setup so only had to download updates once, need to look that up again too.
I have a Steam Library share drive on my Unraid system as well that gets shared with several VMs and systems I have. One Caveat is that occasionally Steam will forget about that setting and say I have no games installed. I just have to go into settings and point the library back to the file share and its working again.
I believe you can do the same for Epic Games but is much more of a hassle because it doesn’t auto discover the installed game. So have to download on one client, then rename the game folder, start download on another, cancel download after 1%, delete new folder, and rename folder back. And do this on each VM. Much a hassle but won’t have to have 4x game files.
Didn’t notice there will be riser cables until now. Make sure they’re properly shielded or you’ll have severe DPC latency issues:
Does this keep working if two people want to play the same game at the same time?
For the most part it does. For the majority of games I played the game just reads the files in game folder. All writing is done in documents where game save files are. But I think Guild Wars 2 has the game in a container and opens the container to play and I had issues with that, or it could of been unrelated account issues. I don’t remember, was just trying to get my wife into MMOs and nothing was working that day, like her interest (lack of) for a fantasy MMO.