Can I Run Nex-N2.5 Pro on Apple M3 Ultra?
Written by Jakub Rusinowski · Last updated September 8, 2026
Yes. Nex-N2.5 Pro needs 244.7 GB at 8K context (239.7 GB weights + 5 GB KV cache/overhead) at Q4_K_M and the Apple M3 Ultra has 384 GB usable, leaving about 139.3 GB of headroom, at roughly 33 tok/s (estimated) with room for up to 256K of context.
See what else this hardware can run →
The numbers
| Model | Nex-N2.5 Pro |
| Parameters | 397B (17B active) |
| Quantization | Q4_K_M |
| VRAM needed (8K context) | 244.7 GB |
| Apple M3 Ultra usable memory | 384 GB |
| Verdict | Runs |
| Max context | 256K |
| Estimated speed | ~33 tok/s |
Nex-N2.5 Pro on the Apple M3 Ultra: VRAM by quantization
| Quant | VRAM needed | Fits 512 GB? | Max context | Whole PC |
|---|---|---|---|---|
| F16 | 799 GB | ✗ No | — | — |
| Q8_0 | 426.8 GB | ✗ No | — | — |
| Q6_K | 330.6 GB | ✓ Yes | 64K | — |
| Q5_K_M | 286.4 GB | ✓ Yes | 128K | — |
| Q4_K_M | 244.7 GB | ✓ Yes | 256K | — |
| Q3_K_M | 174.2 GB | ✓ Yes | 256K | — |
| Q2_K | 135.5 GB | ✓ Yes | 256K | — |
Assumes an 8K-token context with an f16 KV cache, on an estimated architecture — this model publishes no config we can read. A longer window needs more; a quantized KV cache needs less. “Max context” is the largest window that still fits in 512 GB of unified memory. Figures are estimates from parameter count, quantization and memory bandwidth — the analyzer lets you tune KV-cache quant and context.
Context costs VRAM too. At Q4_K_M on the Apple M3 Ultra: 8K 244.7 GB · 32K 257.4 GB · 128K 308.1 GB. Every window this model publishes still fits 512 GB.
What to do next
Nothing to change — run it at Q4_K_M. If you want more capability, check whether the next size up also fits.
No compatible GPU? Nex-N2.5 on 24 GB of system RAM, CPU only: runs, but it is tight.
Running Nex-N2.5 Pro on this card:
Nex-N2.5 Pro needs ~245 GB but this GPU has 512 GB. Rent a 8× H100 (640 GB)-class GPU by the hour instead of buying one:
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Cloud rates verified 2026-07 — estimates, and marketplace prices vary. Buying price is GPU MSRP only, not a full PC.
Other Nex-N2.5 sizes on the Apple M3 Ultra
- Nex-N2.5 Max — does not fit (967.4 GB)
- Nex-N2.5 mini — runs (23.8 GB)
Nex-N2.5 Pro on nearby hardware
- NVIDIA L40S (48 GB) — does not fit
All Nex-N2.5 sizes on the Apple M3 Ultra | Nex-N2.5 Pro model page | Apple M3 Ultra GPU page | VRAM calculator | Check your hardware