Running Qwen 3.8 Flash Next With 130k Context on 16GB VRAM at 15-20 t/s

AvidCyclist250 · reddit · 2026-09-24

After a week of testing, the author shares a full recipe for running Qwen 3.8 Flash Next on an RTX 4080 (16GB VRAM) + 64GB RAM, hitting 15-20 t/s at 130k context.

Four things most people miss: the right quant (AtomicChat AD-4.27bpw / Q4KM target with the shared Unsloth MTP head), the right branch (their pr-mtp-fix branch, i.e. llama.cpp PR #28243 plus one fix commit — plain master can't load this MTP head yet), and the right cache flags (q8 KV cache).

The key trick is --spec-draft-cpu-moe: speculative draft experts live in RAM so the target model's hot experts stay on GPU. Versus 10 t/s with IQ4XS, this setup reaches 16.5 t/s generation / 350 t/s prefill at 131k context. Details in the GitHub repo.

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