Qwen3.8 Flash Next (125B-A6B) on DCU K100-AI 64GB (海光深算) (64GB) — VRAM, KV Cache & Throughput
Qwen3.8 Flash Next (125B-A6B) (125B total, 6B active, Hybrid Linear/Mamba + MoE) uses 70.83 GiB of 4-bit weights (Q4_K_M), requiring 71.65 GiB total at 8K context and 72.21 GiB at 32K on DCU K100-AI 64GB (海光深算) (~69 tok/s decode).
Exceeds Available GPU Memory
Config-derived formula
HF config.json ↗
Required GPU Memory
71.65 GiB
76.93 GB (decimal)
Usable Hardware Memory
60.8 GiB
64 GB (physical)
Safe Headroom
-10.85 GiB
112% utilization
Est. Decode Throughput
~69 tok/s
6B active params
Est. Prefill Throughput
~10617 tok/s
4K Prompt TTFT: ~386 ms
Est. Cost / 1M Tokens
$1.78
Hybrid Linear/Mamba + MoE · Qwen
Recommended Hardware for Current Configuration
Best Single GPU
RTX PRO 6000 Blackwell (96GB)
~$8,500
Best Value / Used GPU
2x A100 80GB SXM
160GB · ~$24,000
Apple Unified Memory
Ryzen AI Max+ 395 128GB
~$1,999
Cloud From
Vast.ai · $0.44 / hr
1x A100 80GB SXM
Production Launch Commands
llama.cpp (GGUF)
llama-server -hf unsloth/Qwen3.8-Flash-Next-GGUF:Q4_K_M \ --ctx-size 8192 -ngl 999 --flash-attn
vLLM
vllm serve Qwen/Qwen3.8-Flash-Next \ --max-model-len 8192 --gpu-memory-utilization 0.92
Live Token Speed Simulator (TTFT ~386ms · ~69 tok/s)
[Qwen3.8 Flash Next (125B-A6B) · 71.65 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.
Purchase break-even
~64.4 months
Est. local power: $12.77 / mo
| Provider | Recommended Instance | Total VRAM | Hourly Rate | Monthly at Selected Hours | Billing Mode | Deploy |
|---|---|---|---|---|---|---|
| RunPod | 1x A100 80GB SXM (Community Cloud · PCIe) | 80 GB | $1.19 / hr | $144.70 / mo | Per-second | Deploy GPU ↗ |
| Vast.ai | 1x A100 80GB SXM (Verified Host · SXM4) | 80 GB | $0.44 / hr | $53.75 / mo | Spot / On-demand | Deploy GPU ↗ |
| Vultr ($300 Free Credit*) | 1x A100 80GB SXM (Dedicated Instance · $300 Credit*) | 80 GB | $2.40 / hr | $291.48 / mo | Hourly | Deploy GPU ↗ |
| Vultr Cloud GPU | 1x A100 80GB SXM (Dedicated Instance) | 80 GB | $2.40 / hr | $291.48 / mo | Hourly | Deploy GPU ↗ |
| DigitalOcean | 1x Instinct MI300X 192GB (Dedicated Instance) | 192 GB | $2.59 / hr | $314.94 / 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) — Qwen3.8 Flash Next (125B-A6B)
QLoRA (4b)
Exceeds Available GPU Memory
73.06 GiB
Model Weights: 70.83 GiB · Gradients + Optimizer: 1.2 GiB · Act: 1.03 GiB
Recommended GPU: RTX PRO 6000 Blackwell (96GB)
LoRA (16b)
Exceeds Available GPU Memory
235.99 GiB
Model Weights: 232.83 GiB · Gradients + Optimizer: 1.8 GiB · Act: 1.36 GiB
Recommended GPU: Instinct MI355X 288GB (288GB)
Full BF16
Exceeds Available GPU Memory
957 GiB
Model Weights: 232.83 GiB · Gradients + Optimizer: 721.77 GiB · Act: 2.4 GiB
Recommended GPU: 8x H200 141GB SXM (1128GB)
Engineering Sizing Notes & Optimization Playbook
Quick Hardware Verdict
A single DCU K100-AI 64GB (海光深算) (64GB) cannot hold 4-bit Qwen3.8 Flash Next (125B-A6B) (71.65 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
Qwen3.8 Flash Next (125B-A6B) uses Hybrid Linear/Mamba + MoE (125B total, 6B active per token). Moving from 8K to 32K context expands FP16 KV cache from 0.26 GiB to 0.82 GiB; enabling 8-bit KV cache (llama.cpp -ctk q8_0 -ctv q8_0 or vLLM --kv-cache-dtype fp8) saves 0.37 GiB at 32K (reducing total VRAM to 71.84 GiB).
VRAM Scaling Across Context Windows (4K to 128K, 4-bit Weights)
Quantization Precision & Memory Matrix — Qwen3.8 Flash Next (125B-A6B) @ 8K
| Quantization Format | Weights (GiB) | KV Cache | Total VRAM (GiB) | Decode Speed | Compatibility (DCU K100-AI 64GB (海光深算)) | Recommended GPU | Data Source |
|---|---|---|---|---|---|---|---|
| Native Weights (BF16 / FP8 / MXFP4 — Lossless) (BF16) | 232.83 GiB | 0.26 GiB | 233.65 GiB (250.88 GB) | ~5.8 tok/s | Exceeds Available GPU Memory | Instinct MI325X 256GB (256GB) | Official checkpoint size |
| FP8 / GGUF Q8_0 (8-bit — Near-Lossless) (Q8_0) | 123.69 GiB | 0.26 GiB | 124.51 GiB (133.69 GB) | ~14.7 tok/s | Exceeds Available GPU Memory | Instinct MI300X 192GB (192GB) | Config-derived formula |
| GGUF Q6_K (6-bit — High Precision) (Q6_K) | 95.46 GiB | 0.26 GiB | 96.28 GiB (103.38 GB) | ~24.9 tok/s | Exceeds Available GPU Memory | Instinct MI300X 192GB (192GB) | Config-derived formula |
| GGUF Q5_K_M (5-bit — Balanced) (Q5_K_M) | 82.93 GiB | 0.26 GiB | 83.75 GiB (89.93 GB) | ~36.7 tok/s | Exceeds Available GPU Memory | RTX PRO 6000 Blackwell (96GB) | Config-derived formula |
| Q4_K_M / UD-Q4_K_XL / AWQ (4-bit — Recommended) (Q4_K_M) | 70.83 GiB | 0.26 GiB | 71.65 GiB (76.93 GB) | ~69 tok/s | Exceeds Available GPU Memory | RTX PRO 6000 Blackwell (96GB) | Config-derived formula |
| GGUF IQ4_XS (4.25-bit — Compact) (IQ4_XS) | 62.03 GiB | 0.26 GiB | 62.85 GiB (67.48 GB) | ~165.5 tok/s | Tight Fit (<8% Headroom) | RTX PRO 6000 Blackwell (96GB) | Config-derived formula |
| GGUF Q3_K_M (3-bit — Low VRAM) (Q3_K_M) | 57.06 GiB | 0.26 GiB | 57.88 GiB (62.15 GB) | ~174.2 tok/s | Fits with Safe Headroom | RTX PRO 6000 Blackwell (96GB) | Config-derived formula |
| GGUF UD-Q2_K_XL (2-bit — Extreme MoE) (UD-Q2_K_XL) | 40.28 GiB | 0.26 GiB | 41.1 GiB (44.13 GB) | ~211.7 tok/s | Fits with Safe Headroom | A40 48GB (48GB) | Config-derived formula |
Technical Specifications & FAQ
Does Qwen3.8 Flash Next (125B-A6B) fit on DCU K100-AI 64GB (海光深算) (64GB)?
In 4-bit (Q4_K_M) at 8,192 context, Qwen3.8 Flash Next (125B-A6B) requires 71.65 GiB total GPU memory (70.83 GiB weights + 0.26 GiB KV cache + 0.56 GiB runtime buffers) against 60.8 GiB usable on DCU K100-AI 64GB (海光深算), delivering ~69 tok/s decode.
How much VRAM does Qwen3.8 Flash Next (125B-A6B) need at 32K context?
At 32,768 context tokens, Qwen3.8 Flash Next (125B-A6B) (Hybrid Linear/Mamba + MoE) allocates 0.82 GiB for KV cache and state, bringing total 4-bit VRAM to 72.21 GiB (77.53 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)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)Gaudi 3 128GB HBM2e (128GB)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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