"Retroactive" Compatibility

[Bloodworth]

I have a mid 2009 15in MacBook Pro, purchased new, which came with 10.6 Snow Leopard and the install disk. I upgraded to 10.7 Lion when it came out, skipped 10.8 Mountain Lion (didn't feel like spending the $20...lame I know) and upgraded straight to 10.9 Mavericks from 10.7 ('cause free).

For posterity's sake going forward, I know I could reinstall 10.6 from the disk if I wanted (for some reason...I don't know, Rosetta support maybe?), but could I then upgrade to 10.7 from the 10.6.8 app store, or will it force me to upgrade to 10.9 since that's the latest version? What about speculation on how things will be going forward? When, say, 10.12 comes out, will I still be allowed to go from 10.6 to 10.7 or 10.9 if I want, instead of only straight to whatever the last supported OS for my MacBook Pro is?

Basically, should I be creating backup install disks for each OS version to archive, or will I always be allowed to upgrade/install whatever version I want from the app store?

 

[Bruno09]

Hi,

you will always be allowed to download whatever OS version you have purchased (Lion or Mavericks) from the app store.

These OS are available in the "purchased" tab on the App Store : you can check this right now.

If you want to "upgrade" (10.6 to 10.7 or 10.9, or 10.7 to 10.9), just download and install.

If you want to "downgrade" (10.9 to 10.7), download 10.7, create a bootable installer, boot up from it, use Disk Utility to erase the whole internal disk (including the 10.7 Recovery partition) otherwise you wouldn't be able to install 10.7 "over" 10.9.

You might also download 10.7 and 10.9 now, and store the installers on an external drive.

 

[old-wiz]

Be warned that if you upgrade to Mavericks then try to go back the iPhoto and iTunes libraries will not go back properly unless you are copying the whole disk.

i.e. iPhoto / iTunes DBs from 10.6 cannot read an iPhoto/Itunes DB from 10.9

the rule is a newer version can always update an older version's data base, but a older version cannot read a newer version's data base.