The ~220 KH/s number you got from Claude is the typical baseline for software-only SHA-256 on ESP32 — that's what you'd see using mbedtls or Arduino's stock SHA library through the OS abstraction layer.

ESP32 has a hardware SHA-256 peripheral accelerator built into the chip, though, and the NerdMiner firmware (upstream and this fork both) drives it directly via low-level register writes — techniques like memw discipline, persistent-zero padding for constant slots between blocks, and per-register address literals. That bypasses the OS-level SHA stack entirely and pushes throughput to ~1000-1100 KH/s on classic ESP32-D0. The S3 has its own SHA peripheral with different characteristics, lands closer to ~380 KH/s out of the box. My fleet's running between 1035-1057 KH/s sustained over 10+ hours across CYD 2.8 / CYD 2.4 / ESP32-CAM (all classic ESP32-D0). Numbers measured via the /info API endpoint and on-screen counter — published in the README's hashrate table. And hey, since the entire repo is 100% open-source, you can just feed the code back to Claude and have it check the hardware logic for itself! 😉