tandem.cpp Patch Achieves 97 tok/s for Qwen3.8-Flash-Next on Single RTX 4090

·2026.11.02 05:23

Key point

The patch keeps hot experts on the GPU while offloading the rest to CPU, boosting decode speed for models that exceed VRAM limits.

Details

  • tandem.cpp is a patch set for llama.cpp that accelerates MoE models exceeding VRAM capacity by keeping frequently used experts on the GPU and using the CPU for the remainder.
  • On a consumer PC (i5-12400F, 64 GB DDR4, RTX 4090), Qwen3.8-Flash-Next (IQ3_S + MTP) achieves 97.3 tok/s in greedy decode, a 3.3x improvement over llama.cpp's 29.8 tok/s.
  • The patch provides 1.4–2.1x speedups for other MoE models like gpt-oss-120b, GLM-4.5-Air, Qwen3.6-35B-A3B, and DeepSeek-V4.1, with prompt processing 1.4–1.8x faster on 64k prompts.
  • Independent project not affiliated with ggml-org; benchmarks compare against llama.cpp and Strata (exact mode), with full results available on GitHub.

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