Trying to install Sequoia for Dual Boot with Tahoe.

Owl-53 wrote:

Interesting. In 2 of 3  cases the Upgrade from Sequoia to Tahoe  seemed to have changed the Controller ibridge Firmware to a newer version 

Subsequent downgrading back to Sequoia is when the firmware mismatch presented issues with the Touch ID functionalities 

The Dual Boot Ventura / Tahoe also Intel T2 configuration . Original installation macOS 13 with added Volume for Tahoe 

For sure the ibridge Firmware was updated during the Tahoe installation. In their case  trying to boot back into Ventura become impossible 

I personally have not encountered any issues on the laptops I've upgraded to Tahoe. I've still been able to boot into older versions of macOS on them without any issues. I know at least two of the laptops I was using TouchID without issues....one was Intel & the other an M1.

Unfortunately the Macs I work with are managed so I have not been able to experiment since some of the recent update patches have been blocked making it very difficult & time consuming for me to experiment for my own curiosity. I'll definitely try to observe the firmware updates now that my organization has unblocked the recent macOS update patches including the ability to even install Tahoe. I'm definitely curious how this works.

Now I have seen issues dual booting even with the same versions of macOS involved which have involved macOS bugs where it has been impossible to boot into an older existing macOS installation (even if the same version) due to this bug as it requires installing macOS over top of itself to fix the problem (or an update patch or complete OS upgrade).

Until your post here, I had not seen or heard of such issues when downgrading macOS although I am aware that there is always a possibility of something being incompatible. And dual booting always has risks & potential problems for a user....even one who is more technical.

HWTech wrote:

Owl-53 wrote:

Interesting. In 2 of 3  cases the Upgrade from Sequoia to Tahoe  seemed to have changed the Controller ibridge Firmware to a newer version 

Subsequent downgrading back to Sequoia is when the firmware mismatch presented issues with the Touch ID functionalities 

The Dual Boot Ventura / Tahoe also Intel T2 configuration . Original installation macOS 13 with added Volume for Tahoe 

For sure the ibridge Firmware was updated during the Tahoe installation. In their case  trying to boot back into Ventura become impossible 

I personally have not encountered any issues on the laptops I've upgraded to Tahoe. I've still been able to boot into older versions of macOS on them without any issues. I know at least two of the laptops I was using TouchID without issues....one was Intel & the other an M1.

Unfortunately the Macs I work with are managed so I have not been able to experiment since some of the recent update patches have been blocked making it very difficult & time consuming for me to experiment for my own curiosity. I'll definitely try to observe the firmware updates now that my organization has unblocked the recent macOS update patches including the ability to even install Tahoe. I'm definitely curious how this works.

Now I have seen issues dual booting even with the same versions of macOS involved which have involved macOS bugs where it has been impossible to boot into an older existing macOS installation (even if the same version) due to this bug as it requires installing macOS over top of itself to fix the problem (or an update patch or complete OS upgrade).

Until your post here, I had not seen or heard of such issues when downgrading macOS although I am aware that there is always a possibility of something being incompatible. And dual booting always has risks & potential problems for a user....even one who is more technical.

To be fair and balanced

Have never tried downgrading nor dual booting when on Intel or M-Class machines

It the observations of 3x incidences, they maybe unique and not as wide spread as it may have been pervious presented

Though, in System Information >> Controller >>   Firmware Version >> iBoot-13822.61.10 is murky and not will documented ( to me ) place

Not something one may take a chance with ?

Thank you again for your invaluable insights and on-hands experiences

A real assist to us all

Duder967 wrote:

I have tried to dual boot Mac OS before and only ended up bricking the Mac.

Lesson learnt

Proceed at your own risk

This is totally possible on compatible Macs—Apple's APFS file system makes it straightforward to install multiple macOS versions on separate volumes without erasing your existing setup.