M6 vs M5 Max vs M5 Ultra: Local LLM Benchmark Showdown – Which Tier Worth Your Money?

Introduction: Which Mac for Local LLMs?

Many users ask which Apple Silicon machine — M6, M5 Max, or M5 Ultra — to buy for running large language models locally. The answer isn't a simple speed comparison; the three tiers differ fundamentally in whether they can fit and run a given model at all.

Quick Verdict: Three Tiers, Three Use Cases

Local LLM value depends on the model size you need to run , not raw benchmark numbers.

M6 (32 GB, 153–170 GB/s) : Runs 14B smoothly, 32B barely; 70B does not fit — entry / daily tier.

M5 Max 128 GB (614 GB/s) : 70B Q4 at 18–32 tok/s — sweet-spot tier.

M5 Ultra 512 GB (1.2 TB/s) : 70B at 35–52 tok/s, 405B at 8–12 tok/s, 120B MoE at 40–155 tok/s — ceiling tier.

In one sentence: M6 is "playable", M5 Max is "enough", M5 Ultra is "unstoppable".

Detailed Breakdown

1. M6: Cheap but Hard Ceiling at 32B

⚠️ M6 launched 11-6; speeds below are projections , not measured.

Bandwidth: 16 GB version only 153 GB/s (same as M5); 24/32 GB versions reach 170 GB/s — buying the small-memory variant wastes the new chip.

Memory caps at 32 GB; using the "memory × 0.7" rule, only ~22 GB is safe for weights.

Measured anchor (entry 16 GB): 9B Q4 ≈ 27 tok/s.

Projected: 27B Q4 ≈ 7–9, 14B ≈ 11–14, 32B Q4 ≈ 5–7 tok/s (32 GB version).

70B Q4_K_M ≈ 42 GB — cannot fit ; serious local LLM work needs at least 32 GB version.

Pricing: Mac mini M6 from ¥6,999; iMac M6 ¥12,499/13,999; MBP14 M6 from ¥15,999.

Conclusion : Fine for coding assistants and daily chat; don't expect to run large models. High price/performance but visible ceiling.

2. M5 Max 128 GB: The Price/Performance Sweet Spot

Must choose the 40-core GPU version (614 GB/s); 32-core version only 460 GB/s — wrong tier loses a chunk of performance.

128 GB unified memory; 70B Q4_K_M (~42 GB) runs comfortably.

70B Q4 measured 18–32 tok/s (MLX higher at 25–32; Ollama/llama.cpp not yet fully utilizing M5 neural engine, mainly bandwidth-bound).

Pricing: Mac Studio M5 Max 128 GB ≈ ¥37,000; MBP16 128 GB top config ≈ ¥41,000.

Conclusion : For serious 70B work without bankruptcy, this is the sweet spot. Silent, portable (MBP), and still usable for other tasks.

3. M5 Ultra 512 GB: Capability Ceiling, Price Ceiling

Four dies, 1.2 TB/s bandwidth , 512 GB memory.

70B Q4 measured 35–52 tok/s ; 120B MoE (e.g., Qwen3.8-125B) 40–155 tok/s (wide range because MoE activates partial experts + concurrency); 405B Q4 8–12 tok/s .

⚠️ Pitfall: macOS defaults to ~75% unified memory for GPU; to run 400B+ models you must run sudo sysctl iogpu.wired_limit_mb=458752 to unlock full memory.

512 GB version goes on sale in China 10-29; official price ¥176,749 (or ¥7,365 × 24 months), 10–12 week delivery.

Conclusion : Only worth it if you need local 405B / full 120B MoE / multi-model concurrency. Ordinary users won't use its memory, but those who need it have no alternative.

Which Tier Fits You?

Only 14B/32B chat & coding → M6 32 GB best value, ~¥10k+, daily use fully covered.

Need fluent 70B + silent & portable → M5 Max 128 GB (Studio ¥37k optimal), 25–32 tok/s no frustration.

Need 405B / full MoE / local agent clusters → M5 Ultra 512 GB (¥177k), but irreplaceable.

⚠️ Don't buy the wrong tier : M5 Ultra 256 GB (~¥100k) and 512 GB share same 1.2 TB/s bandwidth, different memory — double the money for zero speed gain. Want speed? Buy 512 GB. Want savings? Go M5 Max.

The Overlooked Truth: Bandwidth Is the Hard Currency

Decode speed = bandwidth ÷ weight size . Switching engines doesn't change the order of magnitude; adding memory doesn't increase speed — it's a physical limit.

Cost per GB/s bandwidth: M6 cheapest, M5 Max middle, M5 Ultra most expensive but buys capacity , not speed.

Real decision: should your money buy "memory capacity" (how big a model fits) or "bandwidth" (how fast it runs)?

M6 gives capacity without bandwidth; M5 Ultra gives both but at a premium; M5 Max 128 GB balances capacity and bandwidth — that's why it's the best value.

What machine are you on? Drop your model in the comments and I'll estimate what you can run and whether to upgrade.

Data notes: M6 speeds are projections (pre 11-6 launch); M5 Max / M5 Ultra scores aggregated from community llama.cpp / MLX measurements, ranges labeled with quantization and engine differences; prices from China mainland official site / US conversion, vary by configuration.