An advanced benchmark report for running Qwen3.5 locally on RK3588 with source-built llama.cpp: prefill speed, decode speed, stable context, tool-calling behavior, and the practical model choices that actually work on a Radxa ROCK 5B+.
Issue
The usual local-AI advice overemphasizes parameter count and underexplains bandwidth, context budget, KV cache policy, and interactive latency. On RK3588, that leads to bad defaults: models that technically load but feel broken in real chat and tool-calling workloads.
Solution
I ran a corrected Qwen3.5 sweep on RK3588 using source-built llama.cpp, quantized KV cache, and task-pass validation. Then I compared prefill, decode, stable context, average latency, and tool-calling behavior to determine the right model for each workload.