You can install the 64-bit version of Windows 8.1 on a Mac if:
It can run Boot Camp 5.
It meets the system requirements.
You own a valid copy of Windows 8.1 (64-bit), or you already have Windows 8 installed.
Make sure your Mac is compatible with Windows 8.1 by checking this Apple Support page: Boot Camp: Frequently asked questions about installing Windows 8. If your Mac can run Windows 8, then it can run Windows 8.1.
If you don’t have it yet, install Boot Camp 5 (only available on Mac OS X Mountain Lion v10.8.3 and later).
Download the latest drivers from Apple Support.
Install Windows 8.1.
For a clean installation, you'll need to buy Windows 8.1 or Windows 8.1 Pro (64-bit) from a retail store, and use the Boot Camp Assistant to partition your internal hard drive and install Windows 8.1. For more info, see How to perform a clean installation of Windows and the Apple Support page Boot Camp: Frequently asked questions about installing Windows 8.
If you already have Windows 8 installed, you can get the update to Windows 8.1 from the Windows Store for free. See Update to Windows 8.1 from Windows 8.
If you have an earlier version of Windows installed on your Mac, see Upgrade to Windows 8.1 from Windows 7 or Upgrade to Windows 8.1 from Windows Vista or Windows XP.
For more info, visit the Apple Support website.
See all support pages for install, upgrade, & activate.
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