Compatibility Report

• Name of the game with compatibility issues: EzBench
• Steam AppID of the game: 770170

System Information

• GPU: AMD Radeon RX 9070 XT
• Video driver version: Mesa 26.1.6 (RADV)
• Kernel version: Linux 7.1.5-arch1-2
• Link to full system information report as Gist: https://gist.github.com/stanionascu/f094c968dbaf10e8b519e3212bd59606
• Proton version: Proton Experimental

I confirm:

• [x] that I haven't found an existing compatibility report for this game.
• [x] that I have checked whether there are updates for my system available.

Symptoms

The DirectX 12 renderer exhibits significantly lower performance under Proton than both Windows and the DirectX 11 renderer.

Using the default renderer (VKD3D):

• Benchmark starts at approximately 60 FPS and quickly drops to 20–30 FPS.

• MangoHud reports:

  • GPU utilization: ~100%
  • CPU utilization: ~3%
  • Frame time: approximately 30 ms
  • Rendering backend: VKD3D

When forcing DirectX 11 (-dx11 launch option):

• Performance increases to approximately 120 FPS.
• Benchmark score increases to approximately 14,000.

On Windows, the benchmark scores approximately 11,000 on the same hardware.

The issue therefore appears to be isolated to the DirectX 12 / VKD3D rendering path rather than Proton or the graphics stack in general.

System uses:

• AMD Radeon RX 9070 XT
• RADV
• Mesa 26.1.6
• Linux 7.1.5
• Wayland session on COSMIC / KDE

Reproduction

1. Install EzBench (AppID 770170).
2. Run the game with Proton Experimental using the default launch options.
3. Start the benchmark.
4. Observe that the frame rate begins around 60 FPS but quickly falls to approximately 20–30 FPS while GPU utilization remains at ~100%.
5. Exit the game.
6. Add -dx11 to the game's launch options.
7. Run the benchmark again.
8. Observe that performance increases to approximately 120 FPS and the benchmark score rises from roughly 11,000 to 14,000.

Additional observations

• Vulkan is provided by RADV.
• Hardware acceleration is working correctly.
• glxinfo and vulkaninfo both correctly detect the AMD Radeon RX 9070 XT.
• No evidence of CPU bottleneck or software rendering.
• The issue appears specific to the DirectX 12 (VKD3D) rendering path.