Apple M3 Ultra 512GB vs Apple M4 Max 128GB for Local LLMs
The Apple M3 Ultra 512GB holds bigger models (384 GB vs 96.0 GB), and the Apple M3 Ultra 512GB generates tokens about 48% faster. Below: speeds on seven popular models, the models only one card can run, and our verdict.
Specs that matter for AI
| Apple M3 Ultra 512GB | Apple M4 Max 128GB | |
|---|---|---|
| Memory | 512 GB unified | 128 GB unified |
| GPU-usable memory | 384 GB | 96.0 GB |
| Bandwidth | 819 GB/s | 546 GB/s |
| Architecture | Apple Silicon | Apple Silicon |
| Released | 2025-03 | 2024-10 |
| Llama 3.1 8B Q4_K_M | ~95 tok/s | ~64 tok/s |
Speed and fit by model
Q4_K_M (or native format) with 8K context.
| Model | VRAM | Apple M3 Ultra 512GB | Apple M4 Max 128GB |
|---|---|---|---|
| Llama 3.1 8B | 6.3 GB | Fits ~95 tok/s | Fits ~64 tok/s |
| Qwen 3 14B | 10.5 GB | Fits ~54 tok/s | Fits ~36 tok/s |
| gpt-oss-20b | 13.9 GB | Fits ~142 tok/s | Fits ~107 tok/s |
| Qwen 3 30B-A3B | 18.8 GB | Fits ~107 tok/s | Fits ~86 tok/s |
| Qwen 3 32B | 21.4 GB | Fits ~25 tok/s | Fits ~17 tok/s |
| Llama 3.3 70B | 43.2 GB | Fits ~12 tok/s | Fits ~8.0 tok/s |
| gpt-oss-120b | 62.0 GB | Fits ~108 tok/s | Fits ~83 tok/s |
Verdict
The M3 Ultra has four times the memory (about 384 GB GPU-usable) and 50% more bandwidth (819 vs 546 GB/s). It runs models the M4 Max cannot touch, such as Qwen 3.5 397B, MiniMax-M2, DeepSeek V4 Flash and Llama 3.1 405B at Q4. For models up to about 90 GB, the M4 Max is the far cheaper option at about two thirds of the speed.
Which should you buy?
Choose the Apple M3 Ultra 512GB if…
- You want to run 200–400B MoE models at home.
- You want the highest Mac bandwidth.
- You serve models to several people on your network.
Choose the Apple M4 Max 128GB if…
- Your largest model is about 90 GB or less.
- You want a laptop.
- You want to spend far less.
Best quality and longest context on each card
The highest-quality quantization that fits fully at 8K context, and the longest context that fits at Q4_K_M with an FP16 cache.
| Model | Apple M3 Ultra 512GB: best quant | Apple M4 Max 128GB: best quant | Apple M3 Ultra 512GB: max context | Apple M4 Max 128GB: max context |
|---|---|---|---|---|
| Qwen 3.5 9B | FP16 / BF16 | FP16 / BF16 | 256K | 256K |
| Qwen 3 14B | FP16 / BF16 | FP16 / BF16 | 40K | 40K |
| gpt-oss-20b | MXFP4 (official) | MXFP4 (official) | 128K | 128K |
| Qwen 3.6 27B | FP16 / BF16 | FP16 / BF16 | 256K | 256K |
| Qwen 3 32B | FP16 / BF16 | FP16 / BF16 | 40K | 40K |
| Llama 3.3 70B | FP16 / BF16 | Q8_0 | 128K | 128K |
Image generation
Best weight precision for image models with model swapping, at each model's default resolution. Image generation is also limited by compute, so the card with more tensor-core throughput finishes each image faster even when both fit.
| Model | Apple M3 Ultra 512GB | Apple M4 Max 128GB |
|---|---|---|
| SDXL 1.0 | FP16 / BF16 | FP16 / BF16 |
| FLUX.1 [dev] | FP16 / BF16 | FP16 / BF16 |
| Qwen-Image | FP16 / BF16 | FP16 / BF16 |
| Wan 2.2 A14B (T2V / I2V) | FP16 / BF16 | FP16 / BF16 |
Models only one card can run
Only Apple M3 Ultra 512GB
Only Apple M4 Max 128GB
None
Frequently asked questions
Is the Apple M3 Ultra 512GB or Apple M4 Max 128GB better for local LLMs?
The M3 Ultra has four times the memory (about 384 GB GPU-usable) and 50% more bandwidth (819 vs 546 GB/s). It runs models the M4 Max cannot touch, such as Qwen 3.5 397B, MiniMax-M2, DeepSeek V4 Flash and Llama 3.1 405B at Q4. For models up to about 90 GB, the M4 Max is the far cheaper option at about two thirds of the speed.
Which is faster for LLM inference?
The Apple M3 Ultra 512GB, by about 48% for token generation on models that fit both (about 95 vs 64 tokens/s on Llama 3.1 8B Q4_K_M).
Which can run bigger models?
The Apple M3 Ultra 512GB, with 384 GB usable versus 96.0 GB.