gpt-oss 21B (3.6B active)

User reports gpt-oss 20B MXFP4 at 63.3 t/s generation and 700.8 t/s prompt processing on a Mac mini M4 Pro with 64 GB unified memory. Setup is llama.cpp build 6280 with MXFP4 GGUF, F16 K/V cache, flash attention, one Metal device, and -ngl 99. The 63.3 t/s is a separate TG128 depth-zero test, not generation after the four large prompts; prompt rates fall from 700.78 t/s at 2048 tokens to 419.74 t/s at 32768.