Llama 3.1 405B: Meta's Open-Source Answer to GPT-4

The First Open-Source Frontier Model

When Meta released Llama 3.1 405B, it was the first open-source model to credibly compete with GPT-4 across a broad benchmark suite. With 405 billion parameters and a 128k token context window, it brought frontier-level capability to teams who need full control over their model stack.

MMLU score: 88.6% (vs GPT-4 at 86.4% and GPT-4o at 88.7%). On HumanEval (code generation), it scores 89.0% - on par with proprietary alternatives.

License

The Llama 3.1 Community License allows commercial use for products with up to 700 million monthly active users. That covers virtually every startup and enterprise. Companies above that threshold must negotiate a separate agreement with Meta. Full terms at HuggingFace.

Hardware Requirements

The full BF16 model requires approximately 810GB of GPU VRAM - that's 8× H100 80GB GPUs. For most teams, running it through an inference provider (Together AI, Fireworks, Groq) is more practical.

Running Quantized Versions Locally

For local experimentation, GGUF quantized versions via llama.cpp dramatically reduce memory requirements:

# Install Ollama
curl -fsSL https://ollama.com/install.sh | sh

# Pull the quantized 405B (Q4_K_M quantization, ~230GB)
ollama pull llama3.1:405b

# Run a prompt
ollama run llama3.1:405b "Explain the attention mechanism in one paragraph."

For the smaller variants that run on consumer hardware:

# 70B  -  runs on 2× 3090s or A100 40GB
ollama pull llama3.1:70b

# 8B  -  runs on a single 3090 or M2 MacBook Pro
ollama pull llama3.1:8b

Python API via Together AI

from together import Together

client = Together()

response = client.chat.completions.create(
    model="meta-llama/Meta-Llama-3.1-405B-Instruct-Turbo",
    messages=[{"role": "user", "content": "Write a binary search in Rust."}],
    max_tokens=512,
)
print(response.choices[0].message.content)

Comparison to GPT-4

The gap is small. For teams that need data sovereignty, fine-tuning flexibility, or on-premises deployment, Llama 3.1 405B is a compelling GPT-4 alternative.

Summary

Llama 3.1 405B is the benchmark for what open-source models can achieve. Run quantized versions locally with Ollama, access full precision through inference providers, or fine-tune on your own data. Full model weights and instructions at HuggingFace.