User discovers dramatic 665% speed boost using speculative decoding in llama.cpp, with wildly varying results across different models.

Devstrall small model achieved exceptional 665% speed increase with ngram-map-k speculative decoding settings

Gemma 4 31b showed modest 100% speed improvement (doubled token generation) with same configuration

Qwen 3.6 initially delivered only 40% speed gain, but improved to 140% by switching to ngram-mod and adding repeat penalty of 1.0

Different models show vastly different performance improvements with identical speculative decoding parameters, suggesting model-specific optimization needs