Although in recent years when Apple launched a new version of macOS, eligible Mac computers can be upgraded for free, but in the age of OS X, the old Mac must be upgraded to the new system, and it is often necessary to pay for the upgrade. Recently, Apple has fully opened OS X Lion and Mountain Lion, allowing old Mac users to download and install them for free.
OS X Lion and Mountain Lion are OS X 10.7 and 10.8 versions. They can now be downloaded for free on Apple’s official website (OS X Lion, OS X Mountain Lion). OS X Lion supports Intel Core 2 Duo, Core i3, Core i5, Core Mac computer with i7 or Xeon processor, minimum 2GB RAM and 7GB storage space. OS X Mountain Lion supports the corresponding iMac, MacBook, MacBook Pro, Mac mini, Mac Pro and Xserve.
Macs that have built-in OS X Mavericks or later versions are not compatible with the above two system versions. In fact, since Apple released OS X Mavericks (i.e. version 10.9), system upgrades have been changed to free, and the naming method has changed from cats to landmarks in California.