Full installation and operation support spans from legacy versions starting at iOS 12 all the way up to iOS 18.3+. How AmS1gn Handles App Package Formats
When iOS boots, the kernel’s PMCU (Power Management Control Unit) driver verifies the signature of the ams1gn.ipa resident in the /usr/local/standalone/firmware/ directory. If valid, it uploads the payload over a secure SPI bus. The AMS1GN then reboots its internal microcontroller and begins executing the new microcode.