Can the RTX 4070 Laptop 8 GB run Z-Image Turbo?
Download Q6_K (5.9 GB). With the model's working memory it needs about 7.9 GB, leaving 0.1 GB spare on 8 GB. Quality: very close to the original. For better quality, INT8 (6.2 GB) also runs, with about 0.2 GB spilling into system RAM — a little slower, still practical.
Worth trying on this GPU: with an up-to-date ComfyUI, Dynamic VRAM (on by default for NVIDIA since March 2026) streams whatever does not fit from system RAM, and ComfyUI's own start-up message recommends native FP8/INT8 files over GGUF, saying they “will be faster even if they are larger than your memory”. So before settling for a heavily compressed GGUF, try the native INT8 file (6.2 GB). The file recommended above is the best one that fits entirely — the safe choice on older ComfyUI versions, AMD and Intel. Comfy blog: Dynamic VRAM →
01What to download
| Part | File | Folder | Size | |
|---|---|---|---|---|
| Model | z-image-turbo-Q6_K.gguf Q6_K · unsloth/Z-Image-Turbo-GGUF | models/unet | 5.9 GB | Download → |
| Text encoder | qwen_3_4b_fp8_mixed.safetensors Qwen3 4B FP8 · Comfy-Org/z_image_turbo | models/text_encoders | 5.6 GB | Download → |
| VAE | ae.safetensors FLUX.1 VAE (ae) · Comfy-Org/z_image_turbo | models/vae | 0.3 GB | Download → |
| Total download · keep about the same free on disk | 11.9 GB | |||
Alternatives: Qwen3 4B BF16 (8.0 GB). The 16-bit text encoder is a little more faithful; the smaller one is chosen here because it loads faster and needs less RAM. Sizes read from Hugging Face (2026-09-25). “Download” links start the file directly; the file name links are the same files the official ComfyUI workflows use.
System RAM: 32 GB or more. ComfyUI keeps the model file, the text encoder and the VAE in system RAM and moves them to the GPU as needed. With this set of files that is about 11.9 GB, plus roughly 6 GB for Windows, ComfyUI and a browser: 17.9 GB in total. With less RAM it still runs, but Windows starts swapping to disk and loading gets very slow. calculated
02Every Z-Image Turbo file on 8 GB
| File | Size | Needed | On this card | Quality | Download |
|---|---|---|---|---|---|
| 16-bit SAFETENSORS · Comfy-Org | 12.3 GB | 14.3 GB | 6.3 GB too big | the original weights | Hugging Face → |
| Q8_0 GGUF · unsloth | 7.2 GB | 9.2 GB | spills 1.2 GB | practically identical to the original | Hugging Face → |
| INT8 SAFETENSORS · Comfy-Org | 6.2 GB | 8.2 GB | spills 0.2 GB | practically identical to the original | Hugging Face → |
| Q6_K ← GGUF · unsloth | 5.9 GB | 7.9 GB | fits · 0.1 GB spare | very close to the original | Hugging Face → |
| Q5_K_M GGUF · unsloth | 5.6 GB | 7.6 GB | fits · 0.4 GB spare | close; small differences in fine detail | Hugging Face → |
| Q4_K_M GGUF · unsloth | 5.0 GB | 7.0 GB | fits · 1.0 GB spare | good; some loss in fine detail and text | Hugging Face → |
| Q3_K_M GGUF · unsloth | 4.2 GB | 6.2 GB | fits · 1.8 GB spare | noticeable loss of detail | Hugging Face → |
| Q2_K GGUF · unsloth | 3.6 GB | 5.6 GB | fits · 2.4 GB spare | heavy loss; a last resort | Hugging Face → |
Sizes from the Hugging Face file listing, read 2026-09-25. “Needed” = file + 1.2 GB working memory for this model + 0.8 GB kept free for the system.
03The text encoder
Qwen3 4B: 8.0 GB as 16-bit, 5.6 GB as FP8. ComfyUI encodes the prompt first and can push the encoder out of VRAM before sampling, so it does not have to fit together with the model. On 8 GB the FP8 encoder fits on its own, so prompt encoding stays fast.
04About this GPU
The RTX 4070 Laptop 8 GB is an Ada Lovelace GPU with hardware FP8, so ComfyUI can compute Comfy-Org's FP8 files natively: small and fast. (Plain FP8 files use FP8 maths with the --fast fp8_matrix_mult option.) As a laptop GPU it runs at a lower power limit than desktop cards (35–115 W depending on the laptop). The memory verdicts are the same; speed depends heavily on how much power the laptop maker allows.
RTX 4070 Laptop 8 GB: 8 GB GDDR6 · 128-bit · Ada Lovelace · 35–115 W. Everything that runs on the RTX 4070 Laptop 8 GB →
05What more VRAM would change
With 10 GB you could run Z-Image Turbo at 8-bit or better (Q8_0, 7.2 GB) with no offloading: for example on the RTX 3080 10 GB.
What changes from the RTX 4070 Laptop 8 GB to the RTX 3090 24 GB →
06Measured and reported results
Nobody has sent measured numbers for this pair yet. If you run Z-Image Turbo on a RTX 4070 Laptop 8 GB, send your time per image and peak VRAM and it will appear here, credited.
07Questions
How much VRAM does Z-Image Turbo need?
Around 5.6 GB with the smallest file (Q2_K) and 8.2 GB with an 8-bit file (INT8), counting working memory and a small system reserve. The full 16-bit file needs about 14.3 GB.
Which Z-Image Turbo file should I download for the RTX 4070 Laptop 8 GB?
Q6_K (5.9 GB) from unsloth/Z-Image-Turbo-GGUF. Load it with Unet Loader (GGUF) from the ComfyUI-GGUF node pack.
Is FP8 faster than GGUF on the RTX 4070 Laptop 8 GB?
It can be. This GPU has FP8 hardware, and ComfyUI computes FP8 natively for files made for it (Comfy-Org's fp8_scaled files), or for any FP8 file with the --fast fp8_matrix_mult option. GGUF files are unpacked on the fly, which costs some speed.
How much do I need to download for Z-Image Turbo on the RTX 4070 Laptop 8 GB?
About 11.9 GB for the model file, text encoder and VAE listed on this page, and the same again free on disk. With a 8 GB card, 32 GB of system RAM or more is recommended.