DeepSeek V3 671B needs ~497.4 GB but Mac Studio M3 Ultra 256GB only has 184.3 GB. Try a smaller quantization or lighter model.
Operating mode
Interactive favors responsiveness, while light API and scale-out lean harder on serving readiness. The fit stays the same, but the recommendation lens changes.
Current mode
Balanced
Balanced for general local use. Keeps the ranking neutral across personal and serving workflows.
Select quantization to explore
313.1 GB over capacity — needs offload or smaller quantization
Fit status
Too heavy
Decode
2.8 tok/s
TTFT
70198 ms
Safe context
4K
Memory
497.4 GB / 184.3 GB
Offload
60%
Usable shared or unified memory is the main blocker for this model.
Not enough usable memory
The model needs 497.4 GB, but this setup only exposes 184.3 GB of usable shared or unified memory.
Move to a larger memory pool
A larger unified-memory SKU or a discrete high-bandwidth GPU is the cleanest way to make this model practical.
| Workload | Grade | Fit | Decode | TTFT | Context |
|---|---|---|---|---|---|
| Chat | F | Too heavy | 2.8 tok/s | 38290 ms | 4K |
| Coding | F | Too heavy | 2.8 tok/s | 70198 ms | 4K |
| Agentic Coding | F | Too heavy | 2.8 tok/s | 102106 ms | 4K |
| Reasoning | F | Too heavy | 2.8 tok/s | 82961 ms | 4K |
| RAG | F | Too heavy | 2.8 tok/s | 127632 ms | 4K |
How DeepSeek V3 671B (671B params) fits at each quantization level on Mac Studio M3 Ultra 256GB (184.3 GB usable).
| Quant | Bits | VRAM | Quality | Fit |
|---|---|---|---|---|
Q2_K | 2 | 261.7 GB | Low | F0 |
Q3_K_S | 3 | 328.8 GB | Low | F0 |
NVFP4 | 4 |
No, DeepSeek V3 671B requires more memory than Mac Studio M3 Ultra 256GB provides.
DeepSeek V3 671B (671B parameters) requires approximately 497.4 GB of memory with Q4_K_M quantization.
The recommended quantization for DeepSeek V3 671B is Q4_K_M, which balances quality and memory efficiency.
On Mac Studio M3 Ultra 256GB, DeepSeek V3 671B achieves approximately 2.8 tokens per second decode speed with a time-to-first-token of 70198ms using Q4_K_M quantization.
For coding workloads, DeepSeek V3 671B on Mac Studio M3 Ultra 256GB receives a F grade with 2.8 tok/s and 4K context.
On Mac Studio M3 Ultra 256GB, DeepSeek V3 671B can safely use up to 4K tokens of context. The model's official context limit is 131K, but available memory constrains the safe maximum.
Paste this snippet into any page to show a live fit card.
<iframe src="https://willitrunai.com/embed/deepseek-v3-671b-on-m3-ultra-256gb" width="400" height="180" frameborder="0" style="border:none;border-radius:12px;overflow:hidden;" title="Will It Run AI — fit result"></iframe>
Preview:
375.8 GB |
| Medium |
| F0 |
Q4_K_M | 4 | 409.3 GB | Medium | F0 |
Q5_K_M | 5 | 483.1 GB | High | F0 |
Q6_K | 6 | 550.2 GB | High | F0 |
Q8_0 | 8 | 718.0 GB | Very High | F0 |
F16 | 16 | 1375.6 GB | Maximum | F0 |
Move to a larger memory pool. A larger unified-memory SKU or a discrete high-bandwidth GPU is the cleanest way to make this model practical.
Not always. Mac Studio M3 Ultra 256GB can often fit larger models thanks to unified memory, but a discrete GPU with dedicated high-bandwidth VRAM may still decode faster once the model fits. For this combination, the important distinction is capacity versus sustained throughput.
