Mac 
iMac (21.5-inch and 27-inch, Late 2012): Memory specifications
Learn which kinds of memory to use with your iMac (21.5-inch, Late 2012) and iMac (27-inch, Late 2012).
iMac (27-inch, Late 2012): Installing or replacing memory
Learn how to install additional memory or replace the memory in your iMac (27-inch, Late 2012) computer.
iMac (21.5-inch and 27-inch, Late 2012): External features, ports, and connectors
Learn about the external features, ports, and connectors on iMac (21.5-inch and 27-inch, Late 2012) computers.
iMac (21.5-inch and 27-inch, Late 2012), MacBook Pro (Retina, 13-inch, Late 2012): Menu bar may not appear on first login
You may notice that the menu bar does not appear the very first time you log in to a user account on your computer (or after reinstalling Mac OS X). This may occur on iMac (21.5-inch and 27-inch, Late 2012) and MacBook Pro … Continue reading
MacBook Pro (Retina, 13-inch, Late 2012), Mac mini (Late 2012), iMac (21.5-inch, Late 2012): Recommended OS X Software Updates
OS X Software Updates are available and recommended for MacBook Pro (Retina, 13-inch, Late 2012), Mac mini (Late 2012), and iMac (21.5-inch, Late 2012) computers. Learn how to install them with the steps below.
Macbook Pro (Retina, 13-inch, Late 2012): Subtle white lines may appear in Mission Control
When you use Mission Control on your Macbook Pro (Retina, 13-inch, Late 2012), you may notice a few fine lines appear on the desktop. Example:
MacBook Pro (Retina, 13-inch, Late 2012), Mac mini (Late 2012): Recommended OS X Software Updates
OS X Software Updates are available and recommended for MacBook Pro (Retina, 13-inch, Late 2012) and Mac mini (Late 2012) computers. Learn how to install them with the steps below.
OS X Mountain Lion: Firmware updates may keep reappearing in the Mac App Store
When you use a Mac with OS X Mountain Lion, firmware updates may keep appearing in the Mac App Store after you’ve downloaded them. This may occur if the updates download but they don’t automatically start or don’t complete.
MacBook Pro (Retina, Mid 2012): Do not use palm rest covers
Leaving palm rest covers or other material on the palm rest surface of your computer could result in damage to the display when you close it.
