Llama 3.1 405B Instruct on Gaudi 3 128GB HBM2e (128GB) — VRAM, KV Cache & Throughput

Llama 3.1 405B Instruct (405B total, 405B active, Dense GQA) uses 229.51 GiB of 4-bit weights (Q4_K_M), requiring 234.05 GiB total at 8K context and 245.86 GiB at 32K on Gaudi 3 128GB HBM2e (~0.8 tok/s decode).

Interactive Sizing Workbench

Full Compatibility Report →

Open-Weight Model405B / 405B

Weights & QuantizationQ4_K_M · 229.51 GiB

Context Window8,192 (8K)

Target Hardware

128 GB · 3700 GB/s

GPU Count (Tensor Parallel)

Concurrent Batch Size

KV Cache Precision

Inference Engine

System RAM Offload (CPU)0%

Exceeds Available GPU Memory

Config-derived formula HF config.json ↗

Memory Allocation Breakdown (GiB) 234.05 GiB (251.31 GB) / 128 GiB (183%)

Model Weights: 229.51 GiB KV Cache & State: 3.94 GiB Runtime & Activation Buffers: 0.6 GiB System RAM Offload: 0 GiB

Required GPU Memory

234.05 GiB

251.31 GB (decimal)

Usable Hardware Memory

121.6 GiB

128 GB (physical)

Safe Headroom

-112.45 GiB

183% utilization

Est. Decode Throughput

~0.8 tok/s

405B active params

Est. Prefill Throughput

~1178 tok/s

4K Prompt TTFT: ~3477 ms

Est. Cost / 1M Tokens

$2409.72

Dense GQA · Llama 3.1

Recommended Hardware for Current Configuration

Best Single GPU

Instinct MI325X 256GB (256GB)

~$21,000

Best Value / Used GPU

2x H200 141GB SXM

282GB · ~$64,000

Apple Unified Memory

Mac Studio M3 Ultra 512GB

~$9,500

Cloud From

RunPod · $6.94 / hr

1x B300 288GB Blackwell Ultra

Production Launch Commands

llama.cpp (GGUF)

llama-server -hf unsloth/Llama-3.1-405B-Instruct-GGUF:Q4_K_M \
  --ctx-size 8192 -ngl 999 --flash-attn

vLLM

vllm serve meta-llama/Llama-3.1-405B-Instruct \
  --max-model-len 8192 --gpu-memory-utilization 0.92

Live Token Speed Simulator (TTFT ~3477ms · ~0.8 tok/s)

[Llama 3.1 405B Instruct · 234.05 GiB] allocated on target GPU. Prefill completed in TTFT window; streaming autoregressive tokens at memory-bandwidth-bound rate...

Cloud GPU Comparison & Rent-vs-Buy TCO

Verified public rates across RunPod, Vast.ai, Vultr, and DigitalOcean.

Verified: 2026-11-04

Active usage (hours / day)4 h / day

Local hardware budget ($)

Electricity rate ($/kWh)

Purchase break-even

~25.5 months

Est. local power: $21.28 / mo

Provider	Recommended Instance	Total VRAM	Hourly Rate	Monthly at Selected Hours	Billing Mode	Deploy
RunPod	1x B300 288GB Blackwell Ultra (Community Cloud)	288 GB	$6.94 / hr	$843.90 / mo	Per-second	Deploy GPU ↗
Vast.ai	2x H200 141GB SXM (Verified Host · NVL)	282 GB	$7.74 / hr	$940.94 / mo	Spot / On-demand	Deploy GPU ↗
*Vultr ($300 Free Credit)**	8x A100 80GB SXM (Dedicated Instance · $300 Credit*)	640 GB	$19.18 / hr	$2331.80 / mo	Hourly	Deploy GPU ↗
Vultr Cloud GPU	8x A100 80GB SXM (Dedicated Instance)	640 GB	$19.18 / hr	$2331.80 / mo	Hourly	Deploy GPU ↗
DigitalOcean	8x Instinct MI300X 192GB (Dedicated Instance)	1536 GB	$20.72 / hr	$2519.55 / mo	Per-second	Deploy GPU ↗

Rates reflect public listings on the verification date and fluctuate with regional inventory.

Fine-Tuning VRAM Requirements (QLoRA / LoRA / Full) — Llama 3.1 405B Instruct

QLoRA (4b) Exceeds Available GPU Memory

287.67 GiB

Model Weights: 229.51 GiB · Gradients + Optimizer: 56.7 GiB · Act: 1.46 GiB

Recommended GPU: 2x B200 180GB (360GB)

LoRA (16b) Exceeds Available GPU Memory

845.45 GiB

Model Weights: 754.37 GiB · Gradients + Optimizer: 89.1 GiB · Act: 1.98 GiB

Recommended GPU: 8x H200 141GB SXM (1128GB)

Full BF16 Exceeds Available GPU Memory

3096.41 GiB

Model Weights: 754.37 GiB · Gradients + Optimizer: 2338.55 GiB · Act: 3.49 GiB

Recommended GPU: Multi-GPU Required

Engineering Sizing Notes & Optimization Playbook

Quick Hardware Verdict

A single Gaudi 3 128GB HBM2e (128GB) cannot hold 4-bit Llama 3.1 405B Instruct (234.05 GiB at 8K) entirely in VRAM. Use multi-GPU tensor parallelism, offload layers to system RAM, or deploy on a larger cloud GPU.

KV Cache & Runtime Tuning

Llama 3.1 405B Instruct uses Dense GQA (405B total, 405B active per token). Moving from 8K to 32K context expands FP16 KV cache from 3.94 GiB to 15.75 GiB; enabling 8-bit KV cache (llama.cpp -ctk q8_0 -ctv q8_0 or vLLM --kv-cache-dtype fp8) saves 7.87 GiB at 32K (reducing total VRAM to 237.99 GiB).

VRAM Scaling Across Context Windows (4K to 128K, 4-bit Weights)

Model weights remain constant while attention KV cache grows with context length and batch size.

Quantization Precision & Memory Matrix — Llama 3.1 405B Instruct @ 8K

Quantization Format	Weights (GiB)	KV Cache	Total VRAM (GiB)	Decode Speed	Compatibility (Gaudi 3 128GB HBM2e)	Recommended GPU	Data Source
Native Weights (BF16 / FP8 / MXFP4 — Lossless) (BF16)	754.37 GiB	3.94 GiB	758.91 GiB (814.87 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Multi-GPU Required	Official checkpoint size
FP8 / GGUF Q8_0 (8-bit — Near-Lossless) (Q8_0)	400.76 GiB	3.94 GiB	405.3 GiB (435.19 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Multi-GPU Required	Config-derived formula
GGUF Q6_K (6-bit — High Precision) (Q6_K)	309.29 GiB	3.94 GiB	313.83 GiB (336.97 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Multi-GPU Required	Config-derived formula
GGUF Q5_K_M (5-bit — Balanced) (Q5_K_M)	268.7 GiB	3.94 GiB	273.24 GiB (293.39 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Multi-GPU Required	Config-derived formula
Q4_K_M / UD-Q4_K_XL / AWQ (4-bit — Recommended) (Q4_K_M)	229.51 GiB	3.94 GiB	234.05 GiB (251.31 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Instinct MI325X 256GB (256GB)	Config-derived formula
GGUF IQ4_XS (4.25-bit — Compact) (IQ4_XS)	200.99 GiB	3.94 GiB	205.53 GiB (220.69 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Instinct MI325X 256GB (256GB)	Config-derived formula
GGUF Q3_K_M (3-bit — Low VRAM) (Q3_K_M)	184.88 GiB	3.94 GiB	189.42 GiB (203.39 GB)	~0.8 tok/s	Exceeds Available GPU Memory	Instinct MI325X 256GB (256GB)	Config-derived formula
GGUF UD-Q2_K_XL (2-bit — Extreme MoE) (UD-Q2_K_XL)	130.51 GiB	3.94 GiB	135.05 GiB (145.01 GB)	~5.3 tok/s	Exceeds Available GPU Memory	Instinct MI300X 192GB (192GB)	Config-derived formula

Technical Specifications & FAQ

Does Llama 3.1 405B Instruct fit on Gaudi 3 128GB HBM2e (128GB)?

In 4-bit (Q4_K_M) at 8,192 context, Llama 3.1 405B Instruct requires 234.05 GiB total GPU memory (229.51 GiB weights + 3.94 GiB KV cache + 0.6 GiB runtime buffers) against 121.6 GiB usable on Gaudi 3 128GB HBM2e, delivering ~0.8 tok/s decode.

How much VRAM does Llama 3.1 405B Instruct need at 32K context?

At 32,768 context tokens, Llama 3.1 405B Instruct (Dense GQA) allocates 15.75 GiB for KV cache and state, bringing total 4-bit VRAM to 245.86 GiB (263.99 GB decimal).

Evaluate This Model on Other GPUs

RTX 3060 12GB (12GB)RTX 4060 Ti 16GB (16GB)RTX 4070 Ti Super (16GB)RTX 4080 Super (16GB)RTX 5070 12GB (12GB)RTX 5070 Ti (16GB)RTX 5080 (16GB)RTX 3090 (24GB)RTX 4090 (24GB)RTX 4090 D (24GB)RTX 5090 (32GB)RTX 5090 D (32GB)RTX A6000 (48GB)RTX 6000 Ada (48GB)RTX PRO 6000 Blackwell (96GB)DGX Spark (GB10 128GB) (128GB)L4 24GB (24GB)A40 48GB (48GB)L20 48GB (48GB)L40S 48GB (48GB)A800 80GB SXM (80GB)A100 80GB SXM (80GB)H800 80GB SXM (80GB)H100 80GB SXM (80GB)H20 96GB HBM3 (96GB)H20 141GB HBM3e (141GB)H200 141GB SXM (141GB)B200 180GB (180GB)B300 288GB Blackwell Ultra (288GB)Ascend 910B 64GB (昇腾) (64GB)Ascend 910C 128GB (昇腾) (128GB)Atlas 300I Duo 96GB (310P) (96GB)MLU590 80GB (寒武纪思元) (80GB)DCU K100-AI 64GB (海光深算) (64GB)MetaX C500 64GB (沐曦曦云) (64GB)Kunlunxin P800 64GB (昆仑芯) (64GB)MTT S4000 48GB (摩尔线程) (48GB)Radeon RX 7900 XTX 24GB (24GB)Radeon AI PRO R9700 32GB (32GB)Ryzen AI Max+ 395 128GB (128GB)Instinct MI300X 192GB (192GB)Instinct MI325X 256GB (256GB)Instinct MI355X 288GB (288GB)Arc Pro B60 24GB (24GB)Mac mini M4 Pro 64GB (64GB)MacBook Pro M4 Max 128GB (128GB)Mac Studio M4 Ultra 256GB (256GB)Mac Studio M3 Ultra 512GB (512GB)

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