# cu126 PyTorch for Pascal GPUs (CC < 7.5)

ComfyUI's `comfy --skip-prompt install --nvidia` installs the latest cu130
PyTorch build, which only supports compute capability >= 7.5 (Volta and
later). GPUs like the GTX 1050 Ti (CC 6.1, Pascal) produce a cryptic error:

```
RuntimeError: Found GPU0 which is of compute capability (CC) 6.1. The current
PyTorch installation supports... [sm_75, sm_80, sm_86, sm_90, sm_100, sm_120]
```

## Fix

After `comfy install --nvidia`, reinstall torch from the cu126 index:

```bash
/path/to/comfy/ComfyUI/.venv/bin/pip install --force-reinstall \
  torch torchvision torchaudio \
  --index-url https://download.pytorch.org/whl/cu126
```

cu126 supports CC 5.0 and up (sm_50, sm_60, sm_70, sm_75, sm_80, sm_86, sm_90),
covering Pascal, Maxwell, and all later architectures.

## Verify

```bash
/path/to/comfy/ComfyUI/.venv/bin/python -c "
import torch
print(f'CUDA: {torch.cuda.is_available()}')
print(f'Device: {torch.cuda.get_device_name(0)}')
print(f'CC support: {torch.cuda.get_arch_list()}')
"
```

Expected output for GTX 1050 Ti:
```
CUDA: True
Device: NVIDIA GeForce GTX 1050 Ti
CC support: ['sm_50', 'sm_60', 'sm_70', 'sm_75', 'sm_80', 'sm_86', 'sm_90']
```

## Affected GPUs

All Pascal and earlier GPUs:
- GTX 10xx series (1050, 1060, 1070, 1080)
- GTX 9xx and earlier (Maxwell, Kepler, Fermi)
- Any GPU with CC < 7.5

## Why cu126 works

cu12.6 ships with nvidia-cublas, nvidia-cudnn, and all CUDA toolkit
components for multiple CC targets including sm_60. Later CUDA releases
(12.8+) dropped pre-compiled kernels for pre-Volta architectures to reduce
wheel size.