OS X Mountain Lion Installation

OS X Mountain Lion supports several different installation options. It may not be evident when you start the Mountain Lion installer, but you can perform a clean install or an upgrade install of the OS.

You can also install Mountain Lion on a wide range of devices, including your startup drive, an internal partition or volume, or just about any external drive you may have, including USB flash drives.

If you feel up to a bit of fiddling around, you can also create bootable copies of the installer that can run on a DVD, USB flash drive, or any bootable external drive you may have lying around, looking for a purpose in life.

In this article, we've put together a list of all of the OS X Mountain Lion installation options.

OS X Mountain Lion has a few special needs that unfortunately will prevent it from running on some older Intel Macs. Even some Macs that can run OS X Lion may not meet the minimum requirement for Mountain Lion.

This list of the minimum requirements for running Mountain Lion includes the usual data, such as the amount of RAM and disk space you'll need. It also includes a list of Macs that are specifically supported by the Mountain Lion OS.

Make sure your Mac meets the minimum requirements for running OS X Mountain Lion before you get your heart set on installing it.

Minimum Requirements for OS X Mountain Lion
The minimum hardware requirements for OS X Mountain Lion are a bit steeper than the minimum hardware requirements for OS X Lion, its predecessor. Many Macs can work with Mountain Lion, but some Macs won't be able to run anything newer than Lion.

A List of Macs That Will Work With Mountain Lion
iMac - mid 2007 (iMac7,1) or newer
MacBook - late 2008 (MacBook5,1) Aluminum model or newer
MacBook Pro - mid 2007 (MacBookPro3,1) or newer
MacBook Air - 2008 (MacBook Air1,1) or newer
Mac mini - early 2009 (Macmini3,1) or newer
Mac Pro - early 2008 (MacPro3,1) or newer
Xserve - early 2009 (Xserve3,1) model or newer

Apple has been removing Macs that don't support 64-bit processors from its OS X compatibility list since it introduced Snow Leopard. With Mountain Lion, Apple is further trimming the compatibility list by being very strict about what constitutes full 64-bit support.

However, some of the Mac models that didn't make the cut this time, such as earlier versions of the Mac Pro, do have a full 64-bit Intel processor. So, what kept them out of the running?

While the earlier Mac Pros have 64-bit processors, the EFI (Extensible Firmware Interface) boot firmware is 32-bit. Mountain Lion can only boot in 64-bit mode, so any Mac that has 32-bit EFI boot firmware won't be able to run it. Apple can't supply new EFI firmware because the supporting chips for the EFI system in these older Macs are also limited to 32 bits.

If you're not sure if your Mac will make the cut or not, you can find out by following these steps:

If You Use Snow Leopard
  1. Select "About This Mac" from the Apple menu.
  2. Click the More Info button.
  3. Make sure Hardware is selected in the Contents list.
  4. The second entry in the Hardware Overview list is the Model Identifier.
  5. Compare the Model Identifier with the list above. For example, a Model Identifier of MacBookPro5,4 would be eligible to upgrade to Mountain Lion since it is newer than the MacBookPro3,1 identifier in the list.

If You Use Lion
  1. Select "About This Mac" from the Apple menu.
  2. Click the More Info button.
  3. In the About This Mac window that opens, make sure the Overview tab is selected.
  4. The first two entries will include your Mac model and the release date for the model.
You can compare this information against the model list above.

An Alternative Method
There's another way to check whether your Mac can be updated. You can use Terminal to verify that your Mac boots using a 64-bit kernel.
Launch Terminal, which is located in the /Applications/Utilities folder.

Enter the following command at the Terminal prompt:

uname -a

Terminal will return a few lines of text indicating the version of the Darwin kernel this is being used. Look for x86_64 somewhere within the text.
The above process will only work if you're running OS X Lion. If you're still running OS X Snow Leopard, you'll need to force boot into the 64-bit kernel by restarting your Mac while holding down the 6 and 4 keys. Once the Desktop is visible, use Terminal to check for the x86_64 text.

Some Macs that aren't on the list above may still be able to run Mountain Lion, provided they can successfully boot using the 64-bit kernel. This is possible if you've upgraded an older Mac by replacing a logic board, a graphics card, or another major component.

If your Mac can't make the jump to Mountain Lion, you may still want to upgrade to Snow Leopard or Lion, if you haven't already. If your Mac is running the latest OS it can support, you'll be able to receive software updates, and more importantly, security updates, for as long as possible. Apple usually provides security updates for the current version of the OS, as well as the previous two versions of the OS.

Additional Mountain Lion Requirements
8 GB of free hard drive space for the OS installation; more is better, and much more is even better. While 8 GB is enough for the OS and the apps that come with it, there won't be much space left for user data or additional apps. I recommend 60 GB or more for a single user who has a mid to large collection of apps and user data.

2 GB of RAM. Once again, this is the minimum listed by Apple. You will probably want to have at least double that amount of memory, depending on how you use your Mac.

650 MB of additional drive space. Mountain Lion creates a Recovery HD volume on your startup drive. This space is used to hold a bootable system that includes tools for data recovery and the ability to reinstall the OS.

An Internet connection. You'll need the Internet to download the Mountain Lion installer app, and to create your iCloud account when you're setting up Mountain Lion. You'll also need an Internet connection if you ever need to re-install the OS using the Recovery HD volume.