Running a virtual machine with older generations of macOS can have its uses, ranging from security and development to simply being able to run software that won’t work with newer versions of macOS. However, there seems to be a problem when it comes to using a virtual machine in this way on a M4 chip.

Detailed speak Eclectic Light Society. and highlighted by Csaba Fitzl, issues were discovered when trying to run versions of macOS released before macOS 13.4 Ventura in a virtual machine on an M4 Mac. On a M1, M2Or M3Last generation Mac, there is no problem, because this only happens on the M4.

Running the virtual machine with an old macOS installation results in a black screen and boot failure. This turned out to be the case regardless of the settings used for the virtual machine itself, and even in recovery mode.

The actual source of the problem is unknown, due to the inability to access the logs to see what actually happened. There is also no host log failure, everything appearing to be working normally, until the VM failed to boot.

The only real clue discovered is to notice that, despite the allocation of several virtual cores, only one is actually active on the host. It is assumed that the failure occurs at some point in the boot process, before the VM kernel boots the other cores, which occurs at the beginning of the kernel boot phase.

The current best guess is that there is a bug somewhere early in the kernel boot process. This would require fixing the bug in affected macOS kernels and sharing new IPSW image files.

Although this was reported to Apple in comment FB15774587 and reported as affecting UTM, it is unlikely that Apple will do much to resolve this issue. The report writes that Apple probably won’t bother, as it has never released revised IPSWs in this way before.

For anyone who needs to keep older versions of macOS as a virtual machine, the immediate answer is to stick with Mac models running M3 or earlier and give serious thought to future Mac upgrades.