What's the best GPU for running Llama 3.3 70B locally?

Llama 3.3 70B at Q4_K_M needs ~42GB VRAM with an 8K context window — 40GB weights + 2-3GB KV cache. That puts it just outside single-consumer-GPU territory. Three realistic paths:

1. Dual RTX 3090 (~$1,200 used) — the budget winner. 48GB combined VRAM, vLLM tensor parallelism for production serving. Software complexity is real (motherboard PCIe lanes, PSU sizing, case airflow) but the cost-per-GB is unbeatable.

2. RTX 6000 PRO Blackwell 96GB (~$8,000) — the single-card pro path. 96GB means you can run Q6_K_M at 32K context comfortably, or two 32B models concurrently. Premium pricing but zero multi-GPU complexity. Buy this if your time is more expensive than your hardware budget.

3. Mac Studio M3 Ultra 96/192GB (~$4,000-7,000) — the Apple path. Unified memory + MLX gives you usable speed on 70B; community operator reports consistently land in the "comfortably conversational" range, though specific tok/s figures vary by quant, context, and which MLX build you're on — measure on your prompts before sizing. Lower throughput than a 3090 pair but zero noise + zero PSU concerns. Best for solo operators who care about workstation aesthetics.

What NOT to do: single RTX 5090 (32GB) — Llama 3.3 70B Q4 doesn't fit. Single RTX 4090 (24GB) — only Q2/Q3 quants fit and you'll lose noticeable quality. You'll see those configs benchmarked online with reduced context windows, but it's a forced fit.