Dual boot between El Cap and Sierra

[Autistic Behaviour]

I've asked this question already, and googled extensively without clear answers.
My situation: Replaced optical drive with SSD and original HD with another SSD in mbp 13 mid 2012. El cap on my main drive, and, going to test Sierra on my 2nd.

If, theres a efi bootrom update with Sierra, could it negatively affect how my El cap partition works?
Or, are efi bootrom updates meant to be totally backwards compatible with older OS's?

Thanks

 

[Weaselboy]

Or, are efi bootrom updates meant to be totally backwards compatible with older OS's?

No guarantees I suppose, but in previous betas like El Capitan these EFI updates did not cause any issues with the older OS X versions.

I would be surprised if Apple intentionally did anything to break older OS X versions, since you still need to be able to do Internet recovery which gets you the OS that came from the factory.

 

[Autistic Behaviour]

No guarantees I suppose, but in previous betas like El Capitan these EFI updates did not cause any issues with the older OS X versions.

I would be surprised if Apple intentionally did anything to break older OS X versions, since you still need to be able to do Internet recovery which gets you the OS that came from the factory.

Yeah, thats basically what Im thinking....Just irritating that I can't seem to find exact documentation on that particular subject
[doublepost=1465919526][/doublepost]On the other hand, I do recall a few cases where people downgraded efi 1.7 to 1.6, because of problems with negotiated link speeds affected on installed ssd's, so....yeah, never know, I guess....