# ComfyUI + Z-Image Turbo on AMD BC-250 — Complete Setup Guide

> **Hardware**: AMD BC-250 (Cyan Skillfish, gfx1013→gfx1010, 24 CUs, shared RAM)  
> **Backend**: ROCm 7.2.0 / PyTorch 2.5.1+rocm6.2  
> **OS**: CachyOS, kernel 6.18.8-3-cachyos  
> **ComfyUI Version**: 0.15.1  
> **Date**: 2026-03-02

---

## Table of Contents

1. [Overview](#1-overview)
2. [Architecture](#2-architecture)
3. [Prerequisites](#3-prerequisites)
4. [Installation — Step by Step](#4-installation--step-by-step)
5. [Model Setup](#5-model-setup)
6. [Launch Script](#6-launch-script)
7. [ComfyUI Workflow — Z-Image Turbo](#7-comfyui-workflow--z-image-turbo)
8. [BC-250 Specific Tuning](#8-bc-250-specific-tuning)
9. [Troubleshooting](#9-troubleshooting)
10. [File Inventory](#10-file-inventory)
11. [Performance Notes](#11-performance-notes)

---

## 1. Overview

ComfyUI is a node-based Stable Diffusion GUI that runs Z-Image Turbo (a Lumina2-architecture model) via PyTorch with ROCm/HIP on the AMD BC-250 GPU. The model uses a GGUF-quantized diffusion model (Q5_K_S) loaded via the ComfyUI-GGUF custom node, with a Gemma 2 2B text encoder and a Flux-compatible VAE.

### What's Running

| Component | File | Size | Format |
|-----------|------|------|--------|
| Diffusion Model | `z_image_turbo-Q5_K_S.gguf` | 5.2 GB | GGUF Q5_K_S |
| Text Encoder | `gemma2_2b_lumina2.safetensors` | 9.8 GB | Safetensors (f32) |
| VAE | `ae.safetensors` | 335 MB | Safetensors (f32) |

### Pipeline

```
[ComfyUI WebUI :8188] → [PyTorch] → [ROCm/HIP] → [AMD BC-250 GPU]
                                                      ↓
[Gemma 2 2B Text Encoder] → CLIP Encode → [Z-Image Turbo Diffusion] → [VAE Decode] → Image
```

---

## 2. Architecture

### Z-Image Turbo Details

- **Architecture**: Lumina2 (Lumina-Image 2.0 family)
- **Base**: Z-Image by Freepik, turbo-distilled variant
- **Text Encoder**: Gemma 2 2B (Google, 2304-dim embeddings)
- **VAE**: Flux-compatible autoencoder (`ae.safetensors`)
- **Sampler**: Euler with SGM Uniform scheduler, 8 steps (turbo)
- **CFG Scale**: 3.0 (turbo models use low CFG)
- **Latent Format**: Flux-style latent space

### Why GGUF?

The BC-250 has ~14.7 GB shared system RAM. The full FP16 diffusion model would be too large. GGUF Q5_K_S quantization reduces the model from ~12+ GB to 5.2 GB, making it feasible alongside the text encoder and VAE.

---

## 3. Prerequisites

Before starting, you need ROCm working on the BC-250. See `ROCm_BC250_Documentation.md` for the full ROCm setup.

### Required

- ROCm 7.2.0 installed and working (`rocminfo` detects BC-250)
- Python 3.11 (`/usr/bin/python3.11`)
- Git
- ~30 GB free disk space

### Verify ROCm

```bash
rocminfo | grep "Name:"
# Should show: gfx1010 and AMD BC-250
```

---

## 4. Installation — Step by Step

### 4.1 Clone ComfyUI

```bash
cd ~
git clone https://github.com/comfyanonymous/ComfyUI.git
cd ComfyUI
```

### 4.2 Create Python 3.11 Virtual Environment

Python 3.11 is required — Python 3.14 (system default) is too new for PyTorch ROCm wheels.

```bash
python3.11 -m venv venv
source venv/bin/activate
```

### 4.3 Install PyTorch with ROCm Support

```bash
pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/rocm6.2
```

This downloads ~4 GB. The ROCm 6.2 PyTorch wheel is compatible with the ROCm 7.2 runtime.

**Verify installation:**
```bash
python -c "import torch; print(torch.version.cuda); print(torch.cuda.is_available())"
# Should print: 6.2 and True
```

### 4.4 Install ComfyUI Dependencies

```bash
pip install -r requirements.txt
```

### 4.5 Install ComfyUI-GGUF Custom Node

This enables loading GGUF-quantized models in ComfyUI.

```bash
cd ~/ComfyUI/custom_nodes
git clone https://github.com/city96/ComfyUI-GGUF.git
source ~/ComfyUI/venv/bin/activate
pip install gguf
```

### 4.6 Install huggingface-hub (for model downloads)

```bash
pip install huggingface-hub
```

---

## 5. Model Setup

### 5.1 Directory Structure

ComfyUI looks for models in `~/ComfyUI/models/`. Our models live in `~/sd-models/` and are symlinked.

```
~/ComfyUI/models/
├── unet/
│   └── z_image_turbo-Q5_K_S.gguf → ~/sd-models/diffusion_models/z_image_turbo-Q5_K_S.gguf
├── text_encoders/
│   └── gemma2_2b_lumina2.safetensors   (merged from 3 shards, 9.8 GB)
├── vae/
│   └── ae.safetensors → ~/sd-models/vae/ae.safetensors
└── ...
```

### 5.2 Symlink Diffusion Model (GGUF)

The Z-Image Turbo GGUF model must go in `models/unet/` (ComfyUI-GGUF's `UnetLoaderGGUF` node reads from there):

```bash
ln -sf /home/dars/sd-models/diffusion_models/z_image_turbo-Q5_K_S.gguf \
       ~/ComfyUI/models/unet/z_image_turbo-Q5_K_S.gguf
```

### 5.3 Text Encoder — Gemma 2 2B

Z-Image Turbo uses the Gemma 2 2B text encoder from the Lumina-Image-2.0 family. The original model is sharded into 3 safetensors files. We merge them into a single file for ComfyUI.

**Download from Alpha-VLLM (not gated, no login required):**

```bash
source ~/ComfyUI/venv/bin/activate
python3 -c "
from huggingface_hub import hf_hub_download
import os

repo = 'Alpha-VLLM/Lumina-Image-2.0'
dest = os.path.expanduser('~/sd-models/text_encoders/lumina2_gemma2_2b')
os.makedirs(dest, exist_ok=True)

files = [
    'text_encoder/config.json',
    'text_encoder/model.safetensors.index.json',
    'text_encoder/model-00001-of-00003.safetensors',
    'text_encoder/model-00002-of-00003.safetensors',
    'text_encoder/model-00003-of-00003.safetensors',
]
for f in files:
    print(f'Downloading {f}...')
    hf_hub_download(repo, f, local_dir=dest)
print('Done!')
"
```

**Merge shards into single file:**

```bash
source ~/ComfyUI/venv/bin/activate
python3 << 'EOF'
import safetensors.torch
import torch
import os, json

base_dir = os.path.expanduser("~/sd-models/text_encoders/lumina2_gemma2_2b/text_encoder")
output = os.path.expanduser("~/ComfyUI/models/text_encoders/gemma2_2b_lumina2.safetensors")
os.makedirs(os.path.dirname(output), exist_ok=True)

with open(os.path.join(base_dir, "model.safetensors.index.json")) as f:
    index = json.load(f)

all_tensors = {}
shards = set(index["weight_map"].values())
print(f"Loading {len(shards)} shards with {len(index['weight_map'])} tensors...")
for shard in sorted(shards):
    path = os.path.join(base_dir, shard)
    print(f"  Loading {shard}...")
    tensors = safetensors.torch.load_file(path, device="cpu")
    all_tensors.update(tensors)

print(f"Total tensors: {len(all_tensors)}")
print(f"Saving merged file...")
safetensors.torch.save_file(all_tensors, output)
print(f"Done! Size: {os.path.getsize(output)/1e9:.2f} GB")
EOF
```

**Clean up shards (optional):**
```bash
rm -rf ~/sd-models/text_encoders/lumina2_gemma2_2b/
```

### 5.4 VAE

```bash
ln -sf /home/dars/sd-models/vae/ae.safetensors \
       ~/ComfyUI/models/vae/ae.safetensors
```

### 5.5 Verify All Models in Place

```bash
ls -lh ~/ComfyUI/models/unet/*.gguf \
       ~/ComfyUI/models/text_encoders/*.safetensors \
       ~/ComfyUI/models/vae/*.safetensors
```

Expected output:
```
9.8G  ~/ComfyUI/models/text_encoders/gemma2_2b_lumina2.safetensors
5.2G  ~/ComfyUI/models/unet/z_image_turbo-Q5_K_S.gguf  (symlink)
335M  ~/ComfyUI/models/vae/ae.safetensors  (symlink)
```

---

## 6. Launch Script

### Location: `~/start-comfyui.sh`

```bash
#!/bin/bash
# =============================================================
# ComfyUI Launch Script for AMD BC-250 (ROCm / gfx1013)
# =============================================================

set -euo pipefail

echo "=========================================="
echo " ComfyUI — BC-250 ROCm Launcher"
echo "=========================================="

# --- GPU Health Check ---
if dmesg 2>/dev/null | tail -50 | grep -qi "KIQ fence timeout"; then
    echo "[ABORT] KIQ fence timeout detected in dmesg — reboot required!"
    exit 1
fi
echo "[OK] GPU health check passed"

# --- ROCm Environment for BC-250 (gfx1013 → gfx1010 spoof) ---
export HSA_OVERRIDE_GFX_VERSION=10.1.0
export HSA_ENABLE_SDMA=0
export HIP_VISIBLE_DEVICES=0
export ROCM_PATH=/opt/rocm
export HSA_TOOLS_LIB=""
export HSA_TOOLS_REPORT_LOAD_FAILURE=0
export PATH="/opt/rocm/bin:$PATH"
export LD_LIBRARY_PATH="/opt/rocm/lib"

# --- Unset old workaround variables that destroy performance ---
unset GPU_MAX_HW_QUEUES 2>/dev/null || true
unset HIP_LAUNCH_BLOCKING 2>/dev/null || true
unset GGML_CUDA_ENABLE_UNIFIED_MEMORY 2>/dev/null || true
unset GGML_HIP_HOST_ALLOC 2>/dev/null || true
unset GGML_CUDA_NO_PINNED 2>/dev/null || true
unset GGML_HIP_NO_COARSE_GRAIN 2>/dev/null || true
unset HSA_DISABLE_FRAGMENT_ALLOCATOR 2>/dev/null || true

# --- PyTorch ROCm tuning ---
export PYTORCH_HIP_ALLOC_CONF="expandable_segments:False"

echo "[OK] ROCm environment configured"

# --- Activate venv ---
cd ~/ComfyUI
source venv/bin/activate

# --- Launch ComfyUI ---
echo "[START] Launching ComfyUI on http://0.0.0.0:8188"
echo "=========================================="
python main.py \
    --listen 0.0.0.0 \
    --port 8188 \
    --force-fp32 \
    --lowvram \
    "$@"
```

### Usage

```bash
# Foreground (see logs):
bash ~/start-comfyui.sh

# Background with logging:
nohup bash ~/start-comfyui.sh > /tmp/comfyui.log 2>&1 &

# Check if running:
curl -s http://localhost:8188/system_stats | python3 -m json.tool
```

### CLI Flags Explained

| Flag | Why |
|------|-----|
| `--listen 0.0.0.0` | Accept connections from any interface (access from other machines) |
| `--port 8188` | Default ComfyUI port |
| `--force-fp32` | BC-250 gfx1010 has limited FP16 support in PyTorch ROCm; FP32 prevents crashes |
| `--lowvram` | Enables aggressive model offloading — essential for 14.7 GB shared RAM |

---

## 7. ComfyUI Workflow — Z-Image Turbo

### Access the WebUI

Open in browser: **http://localhost:8188** (or `http://<machine-ip>:8188` from another machine)

### Pre-made Workflow

A ready-to-use workflow is saved at:
```
~/ComfyUI/workflows/z_image_turbo_bc250.json
```

Load it via: **Menu → Load → select `z_image_turbo_bc250.json`**

### Manual Node Setup

If building the workflow from scratch, create these nodes:

#### Node 1: UnetLoaderGGUF
- **Type**: `UnetLoaderGGUF` (from ComfyUI-GGUF custom node, category: bootleg)
- **unet_name**: `z_image_turbo-Q5_K_S.gguf`
- **Output**: MODEL → connect to KSampler's "model" input

#### Node 2: CLIPLoader
- **Type**: `CLIPLoader` (built-in, category: advanced/loaders)
- **clip_name**: `gemma2_2b_lumina2.safetensors`
- **type**: `lumina2` ← **CRITICAL: must be set to lumina2**
- **Output**: CLIP → connect to both CLIP Text Encode nodes

#### Node 3: CLIP Text Encode (Positive)
- **Type**: `CLIPTextEncode`
- **text**: Your prompt (e.g., "a beautiful sunset over the ocean")
- **Input**: clip ← from CLIPLoader
- **Output**: CONDITIONING → connect to KSampler's "positive" input

#### Node 4: CLIP Text Encode (Negative)
- **Type**: `CLIPTextEncode`
- **text**: Empty string `""` (turbo models work best with empty negative)
- **Input**: clip ← from CLIPLoader
- **Output**: CONDITIONING → connect to KSampler's "negative" input

#### Node 5: Empty Latent Image
- **Type**: `EmptyLatentImage`
- **width**: `512`
- **height**: `512`
- **batch_size**: `1`
- **Output**: LATENT → connect to KSampler's "latent_image" input

#### Node 6: KSampler
- **Type**: `KSampler`
- **seed**: Any number (42)
- **control_after_generate**: `fixed` (or `randomize` for variety)
- **steps**: `8` (turbo — more steps won't improve quality)
- **cfg**: `3.0` (turbo models use low CFG guidance)
- **sampler_name**: `euler`
- **scheduler**: `sgm_uniform`
- **denoise**: `1.0`
- **Inputs**: model, positive, negative, latent_image
- **Output**: LATENT → connect to VAEDecode

#### Node 7: VAELoader
- **Type**: `VAELoader`
- **vae_name**: `ae.safetensors`
- **Output**: VAE → connect to VAEDecode's "vae" input

#### Node 8: VAE Decode
- **Type**: `VAEDecode`
- **Inputs**: samples (from KSampler), vae (from VAELoader)
- **Output**: IMAGE → connect to SaveImage

#### Node 9: Save Image
- **Type**: `SaveImage`
- **filename_prefix**: `ComfyUI`
- **Input**: images ← from VAEDecode
- Output images saved to: `~/ComfyUI/output/`

### Wiring Summary

```
UnetLoaderGGUF ───MODEL──→ KSampler
CLIPLoader ───CLIP──→ CLIPTextEncode (positive) ──CONDITIONING──→ KSampler
CLIPLoader ───CLIP──→ CLIPTextEncode (negative) ──CONDITIONING──→ KSampler
EmptyLatentImage ──LATENT──→ KSampler
KSampler ──LATENT──→ VAEDecode
VAELoader ──VAE──→ VAEDecode
VAEDecode ──IMAGE──→ SaveImage
```

---

## 8. BC-250 Specific Tuning

### Environment Variables (set in launch script)

| Variable | Value | Why |
|----------|-------|-----|
| `HSA_OVERRIDE_GFX_VERSION` | `10.1.0` | BC-250 (gfx1013) needs gfx1010 spoof for ROCm |
| `HSA_ENABLE_SDMA` | `0` | SDMA engine has hardware bugs on gfx1013 |
| `HIP_VISIBLE_DEVICES` | `0` | Select the BC-250 GPU |
| `ROCM_PATH` | `/opt/rocm` | ROCm installation path |
| `HSA_TOOLS_LIB` | `""` | Disable profiling tools (stability) |
| `HSA_TOOLS_REPORT_LOAD_FAILURE` | `0` | Suppress tool warnings |
| `PYTORCH_HIP_ALLOC_CONF` | `expandable_segments:False` | Prevent memory fragmentation |

### Variables to NEVER Set

These old workarounds **destroy performance** and must NOT be set:

| Variable | Why it's bad |
|----------|-------------|
| `GPU_MAX_HW_QUEUES=1` | Serializes all GPU ops to 1 queue |
| `HIP_LAUNCH_BLOCKING=1` | Forces synchronous kernel launches |
| `GGML_CUDA_ENABLE_UNIFIED_MEMORY=1` | Page fault overhead |
| `GGML_HIP_HOST_ALLOC=1` | Zero-copy over PCIe is slow |

### Memory Considerations

- Total available: ~14.7 GB shared system RAM
- Diffusion model (GGUF Q5_K_S): ~5.2 GB
- Text encoder (Gemma 2 2B f32): ~9.8 GB
- VAE: ~335 MB
- Total model footprint: ~15.3 GB — exceeds available RAM
- **`--lowvram` is essential**: it offloads models to CPU when not in active use
- Only one component is on GPU at a time during inference

### Resolution Recommendations

| Resolution | Latent Size | Notes |
|-----------|-------------|-------|
| 512×512 | 64×64 | Fastest, recommended for testing |
| 768×768 | 96×96 | Good quality, slower |
| 1024×1024 | 128×128 | May OOM on BC-250 |

---

## 9. Troubleshooting

### "KIQ fence timeout" in dmesg → Reboot

```bash
sudo dmesg | grep -i "KIQ fence timeout"
```
If this appears, the GPU is in a bad state. **Reboot the machine.**

### ComfyUI won't start — "No module named torch"

Make sure you activated the venv:
```bash
source ~/ComfyUI/venv/bin/activate
python -c "import torch; print(torch.__version__)"
```

### "CLIP type not found" or wrong model type

Make sure the CLIPLoader node type is set to **`lumina2`** — NOT `stable_diffusion`.

### OOM (Out of Memory) during generation

1. Reduce resolution to 512×512
2. Ensure `--lowvram` is set
3. Close other programs using RAM
4. Try `--use-split-cross-attention` flag

### Model not showing in dropdown

Verify symlinks are not broken:
```bash
ls -la ~/ComfyUI/models/unet/z_image_turbo-Q5_K_S.gguf
ls -la ~/ComfyUI/models/vae/ae.safetensors
ls -la ~/ComfyUI/models/text_encoders/gemma2_2b_lumina2.safetensors
```

### "UnetLoaderGGUF" node not found

Ensure ComfyUI-GGUF is installed:
```bash
ls ~/ComfyUI/custom_nodes/ComfyUI-GGUF/
pip list | grep gguf
```

### PyTorch ROCm version mismatch

```bash
python -c "import torch; print(torch.version.cuda)"
# Should print: 6.2
```

---

## 10. File Inventory

### Installation Files

| File | Purpose |
|------|---------|
| `~/ComfyUI/` | ComfyUI installation directory |
| `~/ComfyUI/venv/` | Python 3.11 virtual environment |
| `~/ComfyUI/custom_nodes/ComfyUI-GGUF/` | GGUF model loader custom node |
| `~/ComfyUI/workflows/z_image_turbo_bc250.json` | Pre-made Z-Image Turbo workflow |
| `~/start-comfyui.sh` | Launch script with ROCm env vars |

### Model Files

| File | Size | Format |
|------|------|--------|
| `~/ComfyUI/models/unet/z_image_turbo-Q5_K_S.gguf` | 5.2 GB | Symlink → `~/sd-models/diffusion_models/` |
| `~/ComfyUI/models/text_encoders/gemma2_2b_lumina2.safetensors` | 9.8 GB | Merged from Alpha-VLLM/Lumina-Image-2.0 |
| `~/ComfyUI/models/vae/ae.safetensors` | 335 MB | Symlink → `~/sd-models/vae/` |

### Output

| File | Purpose |
|------|---------|
| `~/ComfyUI/output/` | Generated images saved here |

### Python Packages (key ones)

| Package | Version |
|---------|---------|
| torch | 2.5.1+rocm6.2 |
| torchvision | 0.20.1+rocm6.2 |
| torchaudio | 2.5.1+rocm6.2 |
| pytorch-triton-rocm | 3.1.0 |
| transformers | 5.2.0 |
| safetensors | 0.7.0 |
| gguf | 0.18.0 |
| comfyui-frontend-package | 1.39.19 |

---

## 11. Performance Notes

### Startup Output (successful launch)

```
Total VRAM 14750 MB, total RAM 15205 MB
pytorch version: 2.5.1+rocm6.2
AMD arch: gfx1010
ROCm version: (6, 2)
Forcing FP32
Set vram state to: LOW_VRAM
Device: cuda:0 AMD Radeon Graphics : native
ComfyUI version: 0.15.1
ComfyUI-GGUF: Partial torch compile only, consider updating pytorch
```

### Expected Timing (BC-250, 512×512, 8 steps)

| Phase | Estimated Time |
|-------|---------------|
| Model Loading (first run) | 30-60s |
| Text Encoding (Gemma 2 2B) | ~2-5s |
| Sampling (8 steps, Euler) | ~60-90s |
| VAE Decode | ~10-15s |
| **Total (first image)** | **~2-3 min** |
| **Total (subsequent)** | **~1-2 min** |

### Comparison with sdcpp-restapi

| | ComfyUI + PyTorch | sdcpp-restapi |
|---|---|---|
| Frontend | Full node-based GUI | REST API + simple WebUI |
| Model format | GGUF + safetensors | GGUF only |
| Memory management | PyTorch (--lowvram) | ggml manual |
| Flexibility | Full workflow customization | Fixed pipeline |
| Turbo steps | Configurable per-run | Config-based |

---

## Appendix: Quick Start Cheatsheet

```bash
# 1. Launch ComfyUI
bash ~/start-comfyui.sh

# 2. Open browser
# http://localhost:8188

# 3. Load workflow
# Menu → Load → z_image_turbo_bc250.json

# 4. Click "Queue Prompt" to generate

# 5. Images saved in ~/ComfyUI/output/
```

---

*Document generated: 2026-03-02 | System: CachyOS + AMD BC-250 + ROCm 7.2.0*