Most inference engines keep 1–3 CPU threads at 100% while serving. Those threads mostly wait: for a GPU kernel, a doorbell or the next step. They wait by polling a flag in a tight loop (spin-wait), because sleeping in the kernel costs tens of microseconds per wake-up.
On GB10 there is a cheaper way to wait. CPU and GPU are cache-coherent over NVLink-C2C, and on the tested
configuration a core parked in the ARM WFE/WFET instruction, with the exclusive monitor armed on the flag's
cache line, was woken by the GPU's store to that line with near-spin latency at much lower power. That
GPU-triggered wake-up is a measured property of this platform, not an architectural guarantee: validate it on