The new desktop OS is somewhat more demanding than OS X
As previous rumors indicated, yesterday Apple renamed its desktop operating system and turned OS X into macOS, but the name wasn’t the only thing to change – the company also switched up the hardware requirements to run the OS.
The new version, macOS Sierra, is slightly more demanding than predecessor OS X El Capitan, and at yesterday’s WWDC keynote, Craig Federighi, senior vice president of software engineering, showed off a slide that detailed the Apple computers which will play nice with the new operating system.
So if you want to run macOS Sierra, when it comes to notebooks, you’ll need a MacBook from late 2009 or better, or a MacBook Air or MacBook Pro from 2010 or later.
If you’ve got an iMac, you’ll be okay with a model from late 2009 or better, and as for the Mac mini or Mac Pro, you’ll need one from 2010 or later to be home and dry with this new macOS.
Sadly, those of you with laptops or computers older than the specified models won’t be getting any Sierra goodness, and will be left mulling a hardware upgrade rather than a software one.
Source: These are the Macs you’ll need to run macOS Sierra | TechRadar