MODEL ARCHITECTURE SPEC • META AI405B Dense
Meta Llama 3.1 405B Instruct VRAM & inference speed
405B Total ParamsDense Architecture126 Layers • 8 KV Heads32K Default Ctx (Max 128K)Ollama: llama3.1:405b
Accurate memory requirements, KV cache footprint, and tokens/sec generation benchmarks for running Meta Llama 3.1 405B Instruct across local GPUs, Apple Silicon Macs, and cloud instances.
✕ OOM260.72 GB (181%)0 t/s
Meta Llama 3.1 405B Instruct on Apple Mac Studio M2 Ultra (192GB Unified Memory)
✕ Out of Memory — Exceeds VRAM Capacity
✕ OOM
Required VRAM
260.72 GB
181% of hardware capacity (144 GB)Est. Decode Speed
0 tok/s
Dense model @ 800 GB/sAvailable Headroom
-116.72 GB
Needs +116.72 GB more VRAMMemory Allocation & Headroom
260.72 GB allocated of 144 GB capacity
181% utilized
Weights: 243 GB
KV: (32K): 8.46 GB
Overhead: 9.26 GB
Deficit: -116.72 GB
⚡ Architecture & Throughput Transparency: Single-user decode speed (~0 tok/s) is memory-bandwidth bound at batch size = 1 on Apple Mac Studio M2 Ultra (192GB Unified Memory) (800 GB/s). Prompt prefill / TTFT (~0 tok/s) is compute-bound and utilizes GPU Tensor cores. Actual latency varies with FlashAttention-2 and runtime engine (Ollama/vLLM/llama.cpp).
OLLAMA_FLASH_ATTENTION=1 OLLAMA_KV_CACHE_TYPE=q8_0 ollama run llama3.1:405b⚠️ Out of VRAM? Don't downgrade model quality.
Out of VRAMSpin up an on-demand cloud GPU instance in 60 seconds with pre-installed Ollama and vLLM. (Meta Llama 3.1 405B Instruct @ 260.72 GB VRAM)
RunPod Cloud GPUsBest 1-Click Ollama & vLLM
$0.34/hr (RTX 4070 Ti) – $2.39/hr (H100)Vast.ai GPU MarketplaceCheapest Dual RTX 3090 / 4090
$0.18/hr (RTX 3060) – $0.55/hr (RTX 4090)Lambda GPU CloudEnterprise 8x H100 Clusters
$1.99/hr (GH200 / H100)Quantization Precision Matrix
32K ctx • KV: Q8_0| Quantization | Weights | KV Cache | Total VRAM | Est. Speed | Fit Status |
|---|---|---|---|---|---|
| FP1616 bpw | 810 GB | 8.46 GB | 847.56 GB (589%) | 0 t/s | OOM |
| Q8_08.5 bpw | 429.3 GB | 8.46 GB | 453.54 GB (315%) | 0 t/s | OOM |
| Q6_K6.56 bpw | 332.1 GB | 8.46 GB | 352.93 GB (245%) | 0 t/s | OOM |
| Q5_K_M5.68 bpw | 287.55 GB | 8.46 GB | 306.82 GB (213%) | 0 t/s | OOM |
| Q4_K_M4.8 bpw | 243 GB | 8.46 GB | 260.72 GB (181%) | 0 t/s | OOM |
| FP44.25 bpw | 214.65 GB | 8.46 GB | 231.37 GB (161%) | 0 t/s | OOM |
| IQ3_XS3.3 bpw | 166.05 GB | 8.46 GB | 181.07 GB (126%) | ~1 t/s | PARTIAL |
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Hardware Compatibility Matrix for Meta Llama 3.1 405B Instruct
Standard Q4_K_M precision with 32K context window and Q8_0 KV cache
| Hardware System | VRAM Envelope | Required VRAM | Headroom | Est. Decode Speed | Compatibility | Test Fit |
|---|---|---|---|---|---|---|
| NVIDIA GeForce RTX 5090 (32GB GDDR7) Consumer GPU • 1792 GB/s | 32 GB | 260.72 GB | -228.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 4090 (24GB GDDR6X) Consumer GPU • 1008 GB/s | 24 GB | 260.72 GB | -236.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| 2x NVIDIA RTX 3090 Dual Rig (48GB Total VRAM) Multi-GPU Rig • 936 GB/s | 48 GB | 260.72 GB | -212.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 5080 (16GB GDDR7) Consumer GPU • 960 GB/s | 16 GB | 260.72 GB | -244.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA RTX 4070 Ti Super (16GB) Consumer GPU • 672 GB/s | 16 GB | 260.72 GB | -244.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 3060 (12GB) Consumer GPU • 360 GB/s | 12 GB | 260.72 GB | -248.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| Apple Mac Mini M4 Pro (64GB Unified Memory) Apple Silicon • 273 GB/s | 54 GB | 260.72 GB | -206.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| Apple Mac Studio M4 Max (128GB Unified Memory) Apple Silicon • 546 GB/s | 112 GB | 260.72 GB | -148.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| Apple Mac Studio M5 Ultra (256GB Unified Memory) Apple Silicon • 890 GB/s | 236 GB | 260.72 GB | -24.72 GB | ~1 tok/s | ⚡ PARTIAL | Test Fit → |
| AMD Strix Halo Mini-PC (Ryzen AI Max+ 395 128GB) Unified APU / Mini-PC • 256 GB/s | 110 GB | 260.72 GB | -150.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA DGX Spark (128GB Grace-Blackwell Unified) AI Appliance • 273 GB/s | 118 GB | 260.72 GB | -142.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA H100 SXM (80GB HBM3 Cloud GPU) Datacenter Cloud GPU • 3350 GB/s | 80 GB | 260.72 GB | -180.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 5070 Ti (16GB GDDR7) Consumer GPU • 896 GB/s | 16 GB | 260.72 GB | -244.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 5070 (12GB GDDR7) Consumer GPU • 672 GB/s | 12 GB | 260.72 GB | -248.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| NVIDIA GeForce RTX 4080 Super (16GB GDDR6X) Consumer GPU • 736 GB/s | 16 GB | 260.72 GB | -244.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| AMD Radeon RX 7900 XTX (24GB GDDR6) Consumer GPU • 960 GB/s | 24 GB | 260.72 GB | -236.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| AMD Radeon RX 7900 XT (20GB GDDR6) Consumer GPU • 800 GB/s | 20 GB | 260.72 GB | -240.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |
| Apple Mac Studio M2 Ultra (192GB Unified Memory) Apple Silicon Workstation • 800 GB/s | 144 GB | 260.72 GB | -116.72 GB | 0 (OOM) | ✕ OOM | Test Fit → |