While working on a Linux port for the latest version of macOS, the team at Asahi Linux has uncovered what they say is a bug in ProMotion MacBooks that could leave users with “a completely unbootable system.”
According to a post on GitHub, the bug is present whether or not you have Asahi Linux installed on your Mac and can be found on versions of macOS Ventura 13.6 and macOS Sonoma 14 and later: “As far as we can tell, ALL users who upgraded to Sonoma the normal way have an out-of-date or even broken System RecoveryOS, and in particular MacBook Pro 14- and 16-inch owners are vulnerable to ending up with a completely unbootable system.”
It apparently has to do with the way macOS Ventura and Sonoma handle refresh rates. As the Asahi team explains, “if the display (on the 14-inch and 16-inch MacBook Pro) is configured to a refresh rate other than ProMotion, that system will no longer be able to boot into older macOS.” Asahi Linux does not support ProMotion.
The developers say this includes recovery mode when those systems are set as the default boot OS, and also System Recovery at least until the next subsequent OS upgrade. The team says users will not lose any data as a result of this bug but will need another Mac to recover from the fault using Device Firmware Upgrade mode.
Granted, this is an issue unlikely to affect many MacBook users, as nearly all of them likely use the ProMotion preset, but if you regularly keep your refresh rate at 60Hz or below, make sure it’s set to ProMotion when upgrading to the newest version of Sonoma.
