Hello everyone,
I’m trying to get ComfyUI working on a new RTX 5070 Ti (Blackwell) GPU under Windows 11.
I’ve already upgraded to the latest PyTorch Nightly with CUDA 12.8 support (which should include Blackwell support).
However, I keep running into this error when running any Triton-based code (e.g., ComfyUI, Stable Diffusion):
ptxas fatal : Value ‘sm_120’ is not defined for option ‘gpu-name’
RuntimeError: ptxas
failed with error code 4294967295
My environment:
- GPU: NVIDIA GeForce RTX 5070 Ti (Blackwell)
- OS: Windows 11 Enterprise x64
- Python: 3.10.6
- PyTorch: 2.8.0.dev20250528+cu128 (Nightly)
- CUDA: 12.9 Toolkit (runtime in PyTorch: 12.8)
- Triton: 3.2.0 (from pip), also tried latest main from
git clone
- ComfyUI: v0.3.34
What I’ve tried:
- Verified single PyTorch install:
pip show torch
(only one, correct version, as above) - Upgraded PyTorch to nightly with CUDA 12.8 as per PyTorch Get Started guide
- Installed CUDA Toolkit 12.9 (system-wide)
- Upgraded Triton (
pip install --upgrade --force-reinstall triton
), only 3.2.0 available via pip - Also did
git clone https://github.com/triton-lang/triton.git
andpip install .
in that folder (which installs 3.2.0) - Did NOT try to build Triton from a specific tag like
v3.3.1
yet (just used the default/main branch) - Cleaned Python caches (
__pycache__
), cleared ComfyUI temp folders - Rebooted after every step
- Drivers updated: NVIDIA 576.52 (latest as of today)
- All software launched from the same Python environment (
where python
andwhere pip
point to the same folder) - Environment variables (
CUDA_PATH
etc) are correct
Questions / Help Needed:
- Is there an official Triton 3.3.1 pip wheel for Windows? (I only see 3.2.0)
- Is it necessary to build Triton from source using the exact 3.3.1 tag for Blackwell support?
If yes, can anyone confirm that ComfyUI / Stable Diffusion / TorchInductor work after that step, on Windows? - Do I need to point PyTorch or Triton to any specific binaries/libraries from CUDA 12.8/12.9?
- Any other tweaks needed for Blackwell GPUs, e.g. editing config files, workarounds, etc.?
Additional info:
- All packages and dependencies are installed in a clean Python 3.10 environment.
- No old PyTorch, CUDA, or Triton left over (I double-checked).
- Still getting the
'sm_120' is not defined for option 'gpu-name'
error (see full log below).
Any help or pointers are very much appreciated.
If someone already has Blackwell GPUs working with the PyTorch Nightly + Triton + CUDA 12.8+ toolchain on Windows, please share your working setup and exact install steps!
Thank you!