qwen397b-nvme-inference

Running 397 Billion Parameters on a Laptop: NVMe-Streamed MoE Inference and Fine-Tuning on 24GB Consumer Hardware

Large language models have outgrown consumer hardware — or so the conventional wisdom goes. We decided to challenge that assumption.

In this post, we present a system that runs Qwen3.5-397B-A17B, a 397-billion parameter Mixture-of-Experts model, entirely on a single Apple MacBook Pro with 24GB of unified memory, achieving 1.77 tokens/second decode throughput — a 7.4x speedup over full MoE inference. We are also the only framework that can run this model on consumer hardware — the only competitor (mlx-lm) is killed by the OS with an out-of-memory error before generating a single token.

We also demonstrate the first fine-tuning of a 400B-class model on consumer hardware, using Sparse MoE-LoRA, training only 0.001% of parameters within a 16GB memory budget.

All code, benchmarks, and trained adapters are open-sourced.

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The Core Problem

Qwen3.5-397B-A17B requires 223GB of storage even after nvfp4 quantization. A data center solves this with high-bandwidth memory and multi-GPU parallelism. A MacBook has 24GB of unified memory and an NVMe SSD.

The key insight: only 17 billion parameters activate per token. The challenge is making the other 223GB of expert weights accessible without loading them into RAM.

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System Architecture

We treat NVMe storage as an extension of the memory hierarchy, streaming expert weights on-demand at ~3.5 GB/s:

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The Central Finding: Most Layers Don't Need Full MoE Routing

Through calibration across all 60 transformer layers, we found that at 32 of 60 layers, the shared expert alone captures >99.5% of output directionality. This enabled a three-tier routing policy:

Expert loads per token drop from 300 to 74 — a 4.1x reduction.

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Optimization Stack: 0.05 → 1.77 tok/s

Time to first token drops from 14.6s to 0.25s (58x improvement).

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Benchmark Results

We evaluated on standard LLM benchmarks. mlx-lm, the only competing framework, crashes with OOM before generating a single token — our system is the only one that runs this model on 24GB hardware.

Quality vs Speed Pareto Frontier:

Knowledge and reasoning benchmarks:

Important caveat on HumanEval/GSM8K: these scores are below the full model's reference (~65% and ~85%). Code generation had the lowest shared-expert agreement (16.7%), and multi-step reasoning compounds small per-layer routing errors. The balanced tier config (PPL 3.00) is recommended for reasoning-heavy tasks.

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Fine-Tuning 397B on a Laptop

By placing LoRA adapters only on the shared expert and the top 15% most-routed experts, trainable parameters drop to just 6.27 million — 0.001% of the full model.

Training on Magicoder-Evol-Instruct-110K, loss dropped from 4.58 to 2.47 over 130 steps (46% improvement), within a 16GB memory budget. Trained adapter: 15KB compressed.

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Repository Contents

├── paper.pdf                    # Research paper
├── engine/                      # Core inference engine
│   ├── inference/
│   │   ├── qwen35_engine.py     # Main Qwen3.5 engine
���   │   ├── expert_cache.py      # LRU expert cache
│   │   ├── experiments.py       # 8 research experiments
│   │   └── ...
│   └── training/
│       ├── moe_trainer.py       # NVMe-streamed trainer
│       └── sparse_lora.py       # Sparse MoE-LoRA
��── scripts/
│   ├── train_coding.py          # Training script
│   └── generate_paper.py        # Paper generation
├── benchmarks/
│   ├── eval_*.py                # All benchmark scripts
│   ├─�� results_*.json           # Benchmark results
│   └── run_all_benchmarks.py    # Master runner
├── adapters/
│   ├── coding_lora.npz          # Trained LoRA adapter
│   └── training_log.json        # Training metrics
├── calibration/
│   └��─ layer_calibration.json   # Tier assignment data
└── tests/                       # Unit tests

Requirements

• Apple Silicon Mac with 24GB+ unified memory
• Python 3.12+
• MLX framework
• Qwen3.5-397B-A17B model weights (nvfp4 quantization, 223GB)

License

MIT