How to read and interpret firmware version numbers from the first Intel Macs to the latest Apple silicon models.
iBoot
Why should an app start crashing on launch in macOS 26.4 beta 2? Why does its firmware version number make no sense? And how did it take 6 months to fix six typos?
Details of new firmware versions for iMac 2019 models, those with T2 or Apple silicon chips. And how Apple assigns version numbers to iBoot.
After the Boot ROM, LLB and iBoot (stage 2), kernel boot starts setting up security services and putting the hardware to work. CPU cores are started up before file systems are mounted, and the Mac starts userspace boot.
Ten years ago, a firmware worm that could have inserted malware into Mac boot flash storage was demonstrated, and shortly afterwards many Macs were found to be running outdated firmware. We’ve come a long way since.
Listing for all compatible Intel Macs with T2 chips, and all Apple silicon Macs.
Explains the sequence of events from Boot ROM to FileVault login, what storage is accessible at different times, and where the code is.
How to check your Mac is booting in Full Security, and how to read its log to verify all the key steps involved in that process.
Gives the latest firmware versions for all Macs running the most recent supported version of macOS, and which are expected to change in the future.
A round-up of firmware updates across 15.4, 14.7.5 and 13.7.5, prospects for future macOS and firmware updates, and problems updating to 15.4.
The Eclectic Light Company 