Benchmarking the new b9200 update: Optimizing Qwen 3.6 27B mtp for Hermes Agent on a single RTX 3090

Reddit r/LocalLLaMA Tools

Summary

Benchmarking the b9200 update of llama.cpp with optimized flags for Qwen 3.6 27B MTP on a single RTX 3090 shows significant performance gains, especially in prompt processing speed, for agentic workflows.

**UPDATED (POST b9200)** Okay the updated version using qwen 3.6 27B mtp gguf from unsloth, running it as the backend for the hermes agent. While dialing it in, I noticed that the currently recommended unsloth mtp flags actually bottleneck performance and tank draft acceptance rates for strict, multi-turn agentic workflows. Pairing a custom config with today's brand new llama.cpp b9200 release — which specifically fixes mtp memory traffic overhead — completely turns that around. Hardware/Software \* RTX 3090 (24GB VRAM) — currently undervolted to keep temps down \* Ryzen 7 5700G / 64GB \* Qwen3.6-27B-IQ4\_NL.gguf \* llama-server (b9200+ compiled from source, commit #23234) \* hermes agent (64K context) max to limit spillover Running the standard recommended mtp flags (--spec-draft-n-max 6 and --spec-draft-p-min 0.75) gave poor results for agentic loops. Generation speeds sat around 7–8 t/s, and the mtp draft acceptance rate hovered around 22–26%. Agent workflows are rigid. A 6-token lookahead frequently guesses the wrong punctuation, the main model rejects the draft, and the GPU throws out the math and recalculates — completely negating the mtp speed boost. Without explicitly declaring parallel slots, llama-server also defaults to 4, eating up memory bandwidth managing unused context slots. The fix and the b9200 boost For agent workflows on a 24GB card, limit to a single slot, drop the lookahead to 3, and remove the p-min threshold so it doesn't hesitate on rigid syntax. Combined with the b9200 release — which stops copying the full logits for every token in the batch during prompt processing — the optimized launch command looks like this: `.\build\bin\Release\llama-server.exe ^ -m D:\models\Qwen3.6-27B-IQ4_NL.gguf ^ --spec-type draft-mtp ^ --spec-draft-n-max 3 ^ --ctx-size 65536 ^ --parallel 1 ^ --flash-attn on ^ --cache-type-k q8_0 ^ --cache-type-v q8_0 ^ --port 8081` Results (Prior to the update vs. Post-b9200) Prior to the update (but with the optimized flags): \* Prompt processing sat around \~560 t/s. \* Token generation hit **17.06 t/s on short tasks and \~9.5 t/s during heavy** context reasoning loops. \* Draft acceptance rate climbed to **77%** (proving a shorter lookahead works better for strict formatting). After the b9200 update: \* Prompt processing jumped to **991+ t/s**. The memory traffic fix paired with --parallel 1 lets the 3090 tear through hermes' massive system prompts. \* Token generation hit a peak of **27.44 t/s** on short tasks and stabilized at a highly usable 13.69 t/s during heavy context loops where the agent is switching between tool calls and main memory. \* Draft acceptance rate maintained a **\~70%** on standard turns. When your VRAM bus isn't clogged by ghost parallel slots or 6-token lookahead rejections, an ***undervolted*** 3090 can still push nearly 30 t/s on a dense 27B model
Original Article

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