GPU Troubleshooting

This guide covers GPU-specific troubleshooting for NVIDIA, AMD, Intel, and other accelerators supported by ComfyUI.

NVIDIA GPU Issues

CUDA not detected or unavailable

Your NVIDIA GPU is not being recognized by PyTorch.Diagnosis: Check if CUDA is available:

import torch
print(torch.cuda.is_available())
print(torch.version.cuda)

Solution:

Update NVIDIA drivers to the latest version

Reinstall PyTorch with CUDA support:

pip uninstall torch torchvision torchaudio
pip install torch torchvision torchaudio --extra-index-url https://download.pytorch.org/whl/cu130

For older GPUs (GTX 10 series), use CUDA 12.6:

pip install torch torchvision torchaudio --extra-index-url https://download.pytorch.org/whl/cu126

Verify CUDA installation:
nvidia-smi

cudaMallocAsync errors or warnings

Async memory allocation may not be supported on your GPU.ComfyUI checks for blacklisted cards and shows a warning if detected.Solution:

python main.py --disable-cuda-malloc

This disables async allocation and uses standard CUDA malloc.

GTX 16 Series (1660, 1650) black outputs or artifacts

GTX 16 series cards have broken FP16 support in their hardware.Solution: Force FP32 computation:

python main.py --force-fp32

This will use more VRAM and be slower, but produces correct results.Affected cards:

GTX 1660 (all variants)
GTX 1650 (all variants)
GTX 1630
T500, T550, T600, T1000, T1200, T2000
MX450, MX550
CMP 30HX

RTX 30/40 Series not using Tensor Cores

Modern NVIDIA GPUs should automatically use optimal precision.Verification: ComfyUI automatically enables FP16 on GPUs with compute capability 8.0+ (RTX 30/40 series).Force optimizations:

python main.py --fast

This enables:

FP16 accumulation for matrix operations
cuDNN auto-tuning for optimal kernels

FP8 Support (RTX 40 series, H100, A100):

python main.py --fp8-e4m3fn-unet

FP8 is automatically used when models are loaded in FP8 format on compute capability 8.9+ GPUs.

Multiple NVIDIA GPUs - selecting specific GPU

Choose which GPU to use when multiple are available.Solution:Set CUDA device:

python main.py --cuda-device 0

Or use environment variable:

CUDA_VISIBLE_DEVICES=1 python main.py

Set default device (reorders device priority):

python main.py --default-device 1

Check available GPUs:

nvidia-smi -L

NVIDIA GPU memory leak or not releasing VRAM

VRAM is not being released after model unloading.Solution:ComfyUI has automatic garbage collection and cache clearing. If issues persist:

Check for circular references in custom nodes (ComfyUI will log warnings about potential memory leaks)
Manually trigger cleanup via the UI or API
Enable deterministic mode to disable some caching:
python main.py --deterministic
Restart ComfyUI to clear all memory

AMD GPU Issues

AMD GPU not detected (Linux)

ROCm is not properly installed or configured.Solution:

Install ROCm following AMD’s official guide

Install PyTorch with ROCm support:

pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/rocm7.1

For latest ROCm 7.2 (may improve performance):

pip install --pre torch torchvision torchaudio --index-url https://download.pytorch.org/whl/nightly/rocm7.2

Verify detection:

import torch
print(torch.version.hip)
print(torch.cuda.is_available())

AMD GPU not detected (Windows - RDNA 3/4)

Windows support for AMD is experimental and limited to RDNA 3, 3.5, and 4.Supported Cards:

RDNA 3: RX 7000 series
RDNA 3.5: Strix Halo, Ryzen AI Max+ 365
RDNA 4: RX 9000 series

Solution:Install architecture-specific PyTorch:RDNA 3 (RX 7000):

pip install --pre torch torchvision torchaudio --index-url https://rocm.nightlies.amd.com/v2/gfx110X-all/

RDNA 3.5 (Strix Halo):

pip install --pre torch torchvision torchaudio --index-url https://rocm.nightlies.amd.com/v2/gfx1151/

RDNA 4 (RX 9000):

pip install --pre torch torchvision torchaudio --index-url https://rocm.nightlies.amd.com/v2/gfx120X-all/

Unsupported AMD GPU architecture override

Older or unsupported AMD GPUs need architecture version override.Solution:For RDNA2 and older (RX 6700, 6600, etc.):

HSA_OVERRIDE_GFX_VERSION=10.3.0 python main.py

For RDNA3 (RX 7600):

HSA_OVERRIDE_GFX_VERSION=11.0.0 python main.py

Older GCN cards (RX 580, Vega): May require specific GFX version. Check your card’s GCN architecture version.

AMD GPU slow performance or crashes

AMD GPUs need specific optimizations for best performance.Solution:

Enable PyTorch Cross Attention (RDNA3+):

TORCH_ROCM_AOTRITON_ENABLE_EXPERIMENTAL=1 python main.py --use-pytorch-cross-attention

Enable TunableOp (first run slow, subsequent faster):
PYTORCH_TUNABLEOP_ENABLED=1 python main.py
For RDNA2 and older, re-enable cuDNN if experiencing issues:
COMFYUI_ENABLE_MIOPEN=1 python main.py
By default, cuDNN is disabled on RDNA3+ for better performance.
Check ROCm version compatibility:
import torch print(torch.version.hip)
- ROCm 7.0+ required for RDNA4
- ROCm 6.4+ recommended for best performance

AMD FP8 support (RDNA4, MI300)

FP8 support on AMD requires specific hardware and software versions.Requirements:

GPU: RDNA4 (RX 9000) or MI300 series
PyTorch: 2.7+
ROCm: 6.4+

Enable FP8: ComfyUI automatically detects FP8 support. To force:

python main.py --fp8-e4m3fn-unet

Verify support: Check console output during startup for “FP8 ops supported” message.

Intel GPU Issues

Intel Arc GPU not detected

Intel XPU support requires specific PyTorch build.Solution:

Install Intel Extension for PyTorch:

pip install intel-extension-for-pytorch

Install PyTorch XPU:

pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/xpu

For latest features:

pip install --pre torch torchvision torchaudio --index-url https://download.pytorch.org/whl/nightly/xpu

Verify detection:

import torch
print(torch.xpu.is_available())
print(torch.xpu.device_count())

Intel Arc performance issues

Intel GPUs benefit from IPEX optimizations.Solution:

IPEX optimization is enabled by default. If experiencing issues:
python main.py --disable-ipex-optimize

Select specific device:

python main.py --oneapi-device-selector "level_zero:0"

Check driver version: Intel frequently updates drivers with performance improvements. Ensure you have the latest Intel graphics drivers.
FP16 support: ComfyUI automatically detects FP16 capability. On older PyTorch (before 2.3), FP16 is always enabled.

Other Accelerators

Ascend NPU (Huawei)

Requirements:

Ascend Basekit (driver, firmware, CANN)
torch-npu package

Installation:

Install Ascend Basekit following official guide
Install torch-npu following installation instructions
Run ComfyUI normally - NPU will be automatically detected

Device Selection:

python main.py --cuda-device 0

(ASCEND_RT_VISIBLE_DEVICES is set automatically)

Cambricon MLU

Requirements:

Cambricon CNToolkit
torch_mlu package

Installation:

Install CNToolkit following official guide
Install PyTorch MLU following installation guide
Run ComfyUI - MLU will be automatically detected

Iluvatar Corex

Requirements:

Iluvatar Corex Toolkit
Compatible PyTorch build

Installation:

Install Iluvatar Corex Toolkit following official documentation
Run ComfyUI - Corex will be automatically detected

DirectML (Not Recommended)

DirectML support is deprecated and may be removed.Warning: DirectML is very slow, hasn’t been updated in over a year, and barely works. Use other options if available.If you must use DirectML:

pip install torch-directml
python main.py --directml 0

Replace 0 with device index. Use -1 for default device.Better alternatives:

Use CPU mode instead: python main.py --cpu
Use WSL2 with CUDA if on Windows with NVIDIA GPU
Use native PyTorch CUDA or ROCm

Apple Silicon (MPS)

Apple Silicon GPU issues

Apple Silicon Macs use Metal Performance Shaders (MPS) for GPU acceleration.Automatic Detection: MPS is automatically detected and used on macOS 12.3+.Known Issues:macOS 14.5+ Black Image Bug: Automatically mitigated by forcing upcast attention:

python main.py --force-upcast-attention

Non-blocking transfers disabled: MPS doesn’t support non-blocking memory transfers due to PyTorch limitation. This is automatic.BF16 support: Available on macOS 14+ with Apple Silicon.Force CPU mode if issues:

python main.py --cpu

VAE on CPU (save VRAM):

python main.py --cpu-vae

General GPU Diagnostics

Check GPU detection and info

At startup, ComfyUI logs:

Total VRAM
Total RAM
Device name and type
PyTorch version
CUDA/ROCm/XPU version
Allocator backend

Enable verbose logging:

python main.py --verbose DEBUG

Check VRAM state: ComfyUI logs the selected VRAM state (HIGH_VRAM, NORMAL_VRAM, LOW_VRAM, etc.).Python script to check detection:

import torch
import comfy.model_management as mm

print(f"Device: {mm.get_torch_device()}")
print(f"Device name: {mm.get_torch_device_name(mm.get_torch_device())}")
print(f"Total VRAM: {mm.get_total_memory() / (1024**3):.2f} GB")
print(f"Free VRAM: {mm.get_free_memory() / (1024**3):.2f} GB")
print(f"VRAM State: {mm.vram_state}")

GPU utilization is low

GPU is not being fully utilized.Common Causes:

CPU bottleneck: Check CPU usage while generating
Slow storage: Loading models from slow drives
Wrong precision: Using FP32 when FP16 is supported
Insufficient VRAM: Models constantly swapping

Solutions:

Enable fast mode:
python main.py --fast

Use appropriate VRAM mode:

python main.py --highvram  # If you have enough VRAM

Enable async offloading:
python main.py --async-offload 2
Check preview method (previews can slow generation):
python main.py --preview-method auto

Temperature or throttling issues

GPU is overheating and throttling performance.Monitor GPU temperature:

NVIDIA: nvidia-smi -l 1
AMD: rocm-smi
Intel: Use system monitoring tools

Solutions:

Improve case airflow
Clean GPU heatsink and fans
Reduce power limit if necessary
Use lower precision to reduce heat:
python main.py --fp16-unet

Note: ComfyUI itself doesn’t cause abnormal heat, but long generation sessions will heat up the GPU normally.

Tutorials

Integration

Troubleshooting

GPU Troubleshooting

NVIDIA GPU Issues

AMD GPU Issues

Intel GPU Issues

Other Accelerators

Apple Silicon (MPS)

General GPU Diagnostics

​NVIDIA GPU Issues

​AMD GPU Issues

​Intel GPU Issues

​Other Accelerators

​Apple Silicon (MPS)

​General GPU Diagnostics

NVIDIA GPU Issues

AMD GPU Issues

Intel GPU Issues

Other Accelerators

Apple Silicon (MPS)

General GPU Diagnostics