The only reason I can think of besides app testing would be if you had a Mac released in late 2013 or early 2014 and you wanted to run macOS 10.9 directly. Turns out I needed a patch to get it to work: For Big Sur there a set of patches too, but I imagine as time goes by it’s harder and harder to patch in support or ignorance of missing hardware features.
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So I used a different Mac to install it, then copied the hard drive. From there you can choose which updates to install… it’s a long, slow process.Īlso note, just as hardware has a minimum OS version it generally has a max version too: I once tried to install a newer copy of macOS on unsupported hardware and was frustrated that the Next button was greyed out or the installer wouldn’t boot. Remember: you can’t install a version of macOS that is older than the hardware - meaning every Mac sold has a version that it shipped with and that’s the minimum version required. I’ve had the most success installing older copies of macOS by using the Recovery Mode to install the copy of the OS that originally shipped, then updating from there to whatever specific version I needed. That’s why they needed special download links, I think? It was the first “free” update, if I recall correctly, and like the updates that followed (10.10, 10.11, 10.12) there were restrictions so only specific computers could download it running specific versions of macOS. My understanding of the App Store link to buy Mavericks is that it only loads of your computer is “old enough” or running 10.7 or 10.8 already. It’s unfortunate that Apple hasn’t made special dmg downloads to allow you to download Mavericks.