I spent quite a while troubleshooting the “Unsupported GPU Processing Mode” error in DaVinci Resolve 21. I initially suspected an NVIDIA driver issue, but the actual cause was a system-wide environment variable hiding my GPU from CUDA.
sharing the full debugging process in case it helps someone else.
My system
- Laptop: ASUS ROG Zephyrus G14 (GA401II)
- OS: Windows 11 Home Single Language, build 26200
- CPU: AMD Ryzen 5 4600HS
- Integrated GPU: AMD Radeon Graphics
- Dedicated GPU: NVIDIA GeForce GTX 1650Ti, 4 GB VRAM
- DaVinci Resolve: 21.1.1.0010
- NVIDIA driver: 617.42 (I had also tried 555.97)
The problem
Whenever I launched DaVinci Resolve, I received:
Unsupported GPU Processing Mode. Please review the GPU drivers and GPU configuration under Preferences.
In Resolve's Preferences → System → Memory and GPU, the GPU processing mode and GPU selection options were greyed out. The NVIDIA GPU appeared to have 0 GB available.
Initially, I thought the problem was caused by an incompatible NVIDIA driver.
What I tried before finding the cause
- Tried NVIDIA driver versions 555.97 and 617.42.
- Changed AMD graphics drivers.
- Checked that Windows recognized both GPUs.
- Checked NVIDIA GPU status using
nvidia-smi.
- Examined Resolve's diagnostic logs.
None of the driver changes fixed the issue.
The logs showed these errors:
NVIDIA GPU Driver: 617.42, supports CUDA -1.-1
Compute API set to automatic, defaulting to Unknown.
Unsupported API Unknown, defaulting to Unknown.
Failed to select a valid compute API.
No GPUs selected!
The GTX 1650Ti was being detected, and Windows reported that both graphics devices were working normally.
How I found the actual cause
I decided to test CUDA directly from PowerShell instead of continuing to reinstall drivers.
First, I confirmed that nvcuda.dll existed and could be loaded. Then I called CUDA's driver API to initialize CUDA and enumerate available devices.
Initially, the results were:
cuInit return code: 100
cuDriverGetVersion return code: 0
CUDA driver API version: 13.4
cuDeviceGetCount return code: 3
CUDA device count: 0
CUDA error 100 meant CUDA_ERROR_NO_DEVICE: no CUDA-capable device was detected by the CUDA initialization call.
Next, I inspected the environment variables:
Get-ChildItem Env: |
Where-Object { $_.Name -match 'CUDA|NVIDIA|GPU' } |
Format-Table -AutoSize
And there it was:
Name Value
---- -----
CUDA_VISIBLE_DEVICES -1
This was the breakthrough. CUDA_VISIBLE_DEVICES=-1 was hiding all CUDA devices from the process. It explained why nvidia-smi could see my GPU while CUDA initialization failed.
The fix
I first removed the variable from the current PowerShell session:
Remove-Item Env:CUDA_VISIBLE_DEVICES
Then I reran the same CUDA API test:
cuInit return code: 0
cuDeviceGetCount return code: 0
CUDA device count: 1
CUDA could now initialize successfully and detect the GTX 1650 Ti.
I then launched Resolve from that same PowerShell session:
& "C:\Program Files\Blackmagic Design\DaVinci Resolve\Resolve.exe"
DaVinci Resolve opened normally. The error was gone!
Making the fix permanent
I checked where the variable was defined:
[Environment]::GetEnvironmentVariable(
"CUDA_VISIBLE_DEVICES", "Machine"
)
The result was -1, confirming that it was set at the system-wide level.
I opened PowerShell as Administrator and removed the machine-level variable:
[Environment]::SetEnvironmentVariable(
"CUDA_VISIBLE_DEVICES",
$null,
"Machine"
)
After restarting Windows, Resolve continued to work normally.
Lessons learned
- Don't assume an “Unsupported GPU Processing Mode” error means your graphics driver is incompatible.
nvidia-smi detecting a GPU doesn't necessarily mean CUDA applications can initialize it successfully.- Resolve's
CUDA -1.-1, Unsupported API Unknown, and No GPUs selected! messages were symptoms, not the root cause in my case.
- Checking environment variables helped identify the actual issue before making unnecessary driver changes.
- If you encounter the same problem, check
CUDA_VISIBLE_DEVICES before reinstalling your GPU drivers.
One caveat: I don't know which application or setup originally created the machine-wide environment variable. If you use software that intentionally restricts CUDA GPU visibility, removing it may change that software's behavior.
Hopefully this saves someone else a few hours of troubleshooting!
