IBoot

iBoot is the name of Apple’s bootloader. Its components are implemented in both hardware and software, and the term iBoot may refer to one of the following, which all have iBoot- in their version strings:
 * Bootrom (SecureROM), the hardware implementation
 * Any of the four variants of the software implementation:
 * iBEC (iBoot Epoch Change; called iBootStage2 in iOS 10 and later)
 * iBoot second-stage loader (often called simply iBoot)
 * iBSS (iBoot Single Stage; called iBootStage1 in iOS 10 and later)
 * LLB (Low Level Bootloader or iBoot first-stage loader in A9 or earlier)

The software implementations are built from the same source, but with different build parameters, as shown in the comparison table below.

* Not included in special development builds

** Included in special development builds

*** Included through the BOOT module, which consists of the submodules FIRMWARE, NVRAM, RAMDISK and SYSCFG.