Compatibility Report

• Name of the game with compatibility issues: Diablo IV
• Steam AppID of the game: 2344520

System Information

• GPU: Steam Deck APU
• Video driver version: 4.6 (compatibility profile) Mesa 24.3.4
• Kernel version: 6.11.11
• Link to full system information report as Gist: https://gist.github.com/cstark27/a92efdb30b27853cb2259e0046ce5104
• Proton version: Experimental (default selected by Steam OS)

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

When using Steam OS frame limiter or in-game vsync with a lowered refresh rate, frametimes vary wildly inconsistently. However, if ‘VKD3D_FRAME_RATE=50 %command%’ is used as a launch option to limit the fps, the frame time graph becomes flat and the fps no longer dips below the desired fps. (DXVK_FRAME_RATE used to be the command but some update made that one stop working).

I have examples with pictures here: https://www.reddit.com/r/SteamDeck/s/IG7d6mp9VI

Reproduction

1. Launch Diablo IV on Steam without any launch options.

2. Enable Vsync in the game options. Set max fps to 150. Set the Steam Deck refresh rate to 50hz. Checkmark the Disable Frame Limit in Steam OS settings (vsync enabled in theory should keep it at 50fps).

3. Teleport to Yelesna and stand still.

4. Observe over the next 60-120 seconds the fps swing from 50fps to 30fps while standing still and nothing of particular interest happening on screen.

5. Exit the game and add the launch option as described above

6. Launch the game without changing any other setting

7. Assuming your character is in the same spot, observe now that your fps and frame time still varies. We’re not done yet.

8. Go to Steam OS QAM and disable the per game profile (or set it back to 90hz refresh rate).

9. Now observe that the fps never dips below 50 anymore. Frame time, while not flat due to the refresh rate mismatch, is now way more consistent.

10. You may also re-enable 50hz refresh rate and disable in-game vsync to have an even smoother graph.

Removing the launch command, lowering the in-game fps limit to 50, disabling vsync and Steam frame rate limiter, is smooth as well. But if you enable vsync you will get the inconsistencies again.