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Industry news, technical articles, and product introductions
📚 Claude Tutorials Hub
40+ step-by-step Claude guides — prompt engineering, Claude Code, API, agents. Browse by topic →
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Part three of my speculative-decoding trilogy on a base Mac mini M4. llama.cpp merged DFlash 2 support with official GGUF drafts — and every configuration is a net slowdown. The README-recommended n-max 7 hits a reproducible Metal OOM on 24GB; the only stable setting cuts prose from 6.0 to 3.0 tok/s, and an 83.8% acceptance rate on code still loses 23%. Same algorithm, same machine, MLX gets 1.8–1.9x. The arithmetic shows why: 0.77s per speculative step loses even at 100% acceptance.
Qwen3.8 ships a trained multi-token-prediction head, and llama.cpp can mount it with one flag — no separate 2B draft model. I benchmarked it against DFlash 2 on the same 24GB Mac mini M4: memory does drop (16.0GB vs 19.4GB peak), but speed goes backwards — prose falls from 6.0 to 4.5 tok/s (-24%) while DFlash 2 delivers 1.8–1.9x on the same machine. Draft acceptance is healthy (59–85%); the loss is in Metal's verify path — batch-8 decode amortizes at just 1.13x, measured.
One week after DFlash 2 shipped, I got Qwen3.8-27B with speculative decoding fully working on a 24GB Mac mini M4: 6.5 tok/s to 11.7–12.2 tok/s at 4-bit, a stable 1.8–1.9x. This post covers the exact deployment commands, three controlled benchmark rounds, the GB-by-GB memory budget, and the three concrete reasons the official 2.7–3.4x number shrinks on consumer Apple Silicon. An Aug 29 retest adds a block-size and draft-precision sweep: block-size 8 collapses to 1.11x (the official cliff warning is real), block-size 3 beats the default, and an 8-bit draft loses to 4-bit.
A 17GB quantized file scores 52 on Artificial Analysis and draws the best local-model pelican ever — yet Simon Willison clocked the same task at 21 minutes on the default setting versus 137 seconds with reasoning off. Here's what Qwen3.8 27B can really do, the quantified evidence of its overthinking, and how to tune reasoning_effort.