The M5 Ultra was running Qwen3.8 Flash Next at less than half the speed the hardware allows, the software was the problem; NOT ANYMORE!!!!
To write one word, the model has to read its weights from memory. On this Mac that takes 5.2 ms, so in theory it could write about 190 words per second.
In practice each word took 12.9 ms, about 78 words per second. The GPU was busy the whole time, just not doing useful work.
After we merged the work into fewer, bigger steps, each word now takes 9.5ms. Still room to go but we're getting there!