Dense or MoE for Qwen 3.5 Local Runs?
๐กPractical hardware advice for running Qwen 3.5 locally on high-end GPUs
โก 30-Second TL;DR
What Changed
Current setup: dual AMD 7900XT (40GB VRAM, 800GB/s) runs Qwen 3.5 27B slowly for coding.
Why It Matters
Highlights trade-offs in local LLM inference between memory capacity for large MoE models and bandwidth for dense models, aiding hardware decisions for developers.
What To Do Next
Benchmark Qwen 3.5 27B inference speed on your GPU before upgrading to RTX 5090.
๐ง Deep Insight
Web-grounded analysis with 8 cited sources.
๐ Enhanced Key Takeaways
- โขQwen3.5-27B employs a dense architecture with 64 layers, hidden dimension of 5120, 24 attention heads (4 KV heads), RMS normalization, and SwigLU activation, activating all 27B parameters per forward pass[1].
- โขQwen3.5-27B achieves top benchmarks including MMLU-Pro 86.1%, GPQA Diamond 85.5%, SWE-bench Verified 72.4%, and supports 262k native context extensible to 1M across 201 languages[1][4].
- โขDense Qwen3.5-27B outperforms MoE variant Qwen3.5-35B-A3B in complex coding and reasoning (e.g., 7.5 t/s vs 46 t/s on similar hardware, but superior logic depth)[3][5].
- โขOn 24GB VRAM GPUs like RTX 4090, Qwen3.5-27B runs at Q6/Q8 quantization for high quality, requiring ~16-18GB at Q4[3].
๐ Competitor Analysisโธ Show
| Feature | Qwen3.5 27B (Dense) | Qwen3.5 35B-A3B (MoE) |
|---|---|---|
| Total Parameters | 27B | 35B |
| Active Parameters | 27B | ~3B |
| Tokens/s (RTX 3090) | 15-25 | 60-100 |
| VRAM Q4 | 16-18GB | 20-22GB |
| Best For | Coding/Logic | Fast Chat[3] |
๐ ๏ธ Technical Deep Dive
- โขArchitecture: Dense model with Gated Delta Networks (GDN) and Feed Forward Networks; hidden layout 16 ร (3 ร (Gated DeltaNet โ FFN) โ 1 ร (Gated Attention โ FFN))[2].
- โขAttention: Grouped-Query Attention with 24 Q-heads (head dim 256), 4 KV-heads (head dim 128), Rotary Position Embedding (ROPE) dim 64[1][2].
- โขFFN: Intermediate dimension 17408, SwigLU activation, RMS Normalization[1][2].
- โขMultimodal: Unified vision-language capabilities, supports 201 languages, 262k context (ext. 1M)[1].
- โขQuantization: Runs on consumer GPUs; Q4 needs ~16GB VRAM, Q6/Q8 on 24GB GPUs[3].
๐ฎ Future ImplicationsAI analysis grounded in cited sources
โณ Timeline
๐ Sources (8)
Factual claims are grounded in the sources below. Forward-looking analysis is AI-generated interpretation.
- apxml.com โ Qwen35 27b
- Hugging Face โ Qwen3.5 27b
- vertu.com โ Qwen 3 5 27b vs Qwen 3 5 35b A3b Which Local LLM Reigns Supreme
- developer.puter.com โ Qwen3.5 27b
- sonusahani.com โ Qwen 27b vs Qwen 35b
- ollama.com โ Qwen3.5:27b
- artificialanalysis.ai โ Qwen3 5 122b A10b vs Qwen3 5 27b
- qwen.ai โ Blog
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Original source: Reddit r/LocalLLaMA โ