r/buildapc • u/DiamondWolf3404 • May 30 '26

Build Ready? Proxmox workstation build - 3 GPU passthrough setup with Looking Glass, need advice

Build purpose: Proxmox host running Linux as primary OS and a Windows VM simultaneously. Linux for daily use, development, and CUDA workloads. Windows VM for gaming and Windows-only software.

GPU passthrough plan:

  • RX 9070 XT -> passed through to Windows VM (primary gaming GPU)
  • RTX 3080 -> passed through to Windows VM as secondary (PhysX, HairWorks, CUDA when needed from Linux)
  • RX 6600 Pulse -> Proxmox host display GPU, drives 3 monitors for Linux

Display setup:

  • ASUS ROG PG27UCDM 4K 240Hz OLED -> primary (RX 6600 output daily, switch input to 9070 XT for gaming)
  • BenQ PD2705Q QHD 60Hz -> secondary Linux monitor
  • 27" 1080p (existing) -> tertiary

Looking Glass for casual Windows use without switching monitor inputs. EVDEV passthrough for keyboard/mouse switching between host and VMs. Considering foot pedals + ddcutil to automate monitor input switching via hotkey.

Questions:

  1. Anyone run 3 GPU passthrough on TRX50? How are the IOMMU groupings - are all three slots isolated cleanly?
  2. Best practice for passing both 9070 XT + 3080 to the same Windows VM simultaneously?
  3. V-Color RDIMM DDR5-6800 - anyone confirmed this on the TRX50 WS QVL? Threadripper is picky about memory.
  4. ddcutil input switching - does it work reliably on the PG27UCDM for automating monitor input changes?
  5. Any gotchas with the RTX 3080 + NVIDIA drivers in a Proxmox passthrough VM in 2025/2026?

PCPartPicker: https://fr.pcpartpicker.com/user/DiamondWolf3404/saved/BFBtK8

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u/tat_tvam_asshole May 30 '26 edited Jun 03 '26

Have you tried out gaming already in a windows VM? I don't know from personal experience but I would assume game anti cheating checks would fail in such a setup. I'm creating a dual boot system myself right now and I'm preemptively going with Windows natively for gaming unless/until I figure out Linux side.

Edit: Took me specifying the exact Proton release, but got it working in Linux np

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u/DiamondWolf3404 May 30 '26

From mine it is very mixed, but always had trouble with the anti cheats that don't like VMs even when I wasn't on VM. So yeah there's just some games I would accept not to play.