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This chapter is from the book

This chapter is from the book

What You Need to Install and Run Mac OS X

Well, for starters you need the Mac OS X Install CDs or DVD. Beyond that, keep reading. . .

Which Mac models can run Mac OS X?

Apple's official position is that only Macs with the following specifications can run Mac OS X 10.4.x (Tiger); older and newer versions of Mac OS X may have different requirements:

  • PowerPC G3, G4, or G5 processor
  • Built-in FireWire ports
  • At least 256 MB of RAM (although the more, the better)
  • A built-in display or a display connected to an Apple-supplied video card supported by your computer (in other words, Apple doesn't officially support a Mac running a third-party video card)
  • 3 GB or more of free hard-drive space (4 GB or more if you install the Xcode Developer Tools)

Older versions of Mac OS X supported older Power Macs, iMacs, and PowerBooks. Tiger does not.

If you're uncertain of your own Mac's processor, select About This Mac from the Apple menu and check the Processor line.


Figure 3.1 The About This Mac window shows that this Mac is a Power Mac G5 with 2 GB of RAM and is running Mac OS X 10.4.2.

Does this mean that you absolutely cannot use Mac OS X on an older Mac—even one that's been upgraded to include a G4 processor (such as a Power Mac 7500 with a processor upgrade)? Apple's position remains firm: You cannot run Mac OS X on these Macs. However, some users (who won't take no for an answer!) have found ways to run Mac OS X on at least some of these older Macs. If you're willing to give it a shot, the utility XPostFacto, from Other World Computing (, provides a good starting point. Be aware, however, that if you have any problems running Mac OS X on these systems, Apple will not help you solve them. For that reason, I strongly recommend that if you want to run Mac OS X, get a Mac that's sanctioned to run it.

How much memory do you need?

If you know your Mac can run Mac OS X, your next step is to make sure it has enough memory (RAM) installed. Without sufficient RAM, Mac OS X may run, but performance may be unacceptably slow—to the point where the OS may seem to freeze at times.

Apple says you need at least 256 MB of memory to use Mac OS X. Consider this figure to be a bare minimum. To get the best performance from Mac OS X, I recommend at least 512 MB—more, ideally.

Every Mac can accommodate more memory than the minimum that ships from Apple. Typically, you add memory by purchasing a memory module and inserting it into the designated RAM slot(s) on your Mac. Each Mac model comes with instructions on how to do this, and Apple makes sure that the process is easy (the Mac mini is an exception here; just opening the case is a bit tricky).

How much hard-drive space do you need?

Apple says you should have a minimum of 3 GB of free space on your hard drive before attempting to install Mac OS X (4 GB if you intend to install the developer software). (Note: The amount of "available" hard-drive space on a volume is shown in the status bar of the Finder window for any folder on that volume.) However, Mac OS X runs best when you have a good deal more unused space. Given the size and price of today's hard drives, I recommend that you make sure you have at least 6 GB of unused space on your Mac OS X volume after Mac OS X and any additional software have been installed.


Figure 3.2 The amount of disk space available for a volume, as viewed in the status bar at the bottom of a Finder window.

We'll return to the issue of hard-drive space later in the chapter when I cover the pros and cons of partitioning a drive.

Will you be installing Mac OS 9?

Mac OS 9 applications are able to run seamlessly within Mac OS X—a capability derived from Mac OS X's Classic-environment feature (which you can learn more about in the online Classic chapter). To take advantage of this capability, however, you must have Mac OS 9 installed somewhere on your drive. If you're running Mac OS X 10.2 Jaguar or later, you need Mac OS 9.2.x installed.

If you don't know which version of Mac OS X is installed on your computer, just choose the About This Mac item from the top of the Apple menu. The window that opens provides this information. Similarly, to determine the version of Mac OS 9, select About This Computer from the Apple menu that appears when a Classic application is active in Mac OS 9 or when your computer is booted from Mac OS 9. Otherwise, you can check the version number by opening the Mac OS 9 System Folder, selecting Get Info (Command-I) for the System or Finder file, and checking the version information. If Classic is running, you can also get this information from the Memory/Versions pane of the Classic System Preferences.

Currently shipping Macs do not come with a Mac OS 9 System Folder preinstalled. If you want to install Mac OS 9, you'll need to use a Mac OS 9 Install CD (if you have one) or the disc containing Mac OS 9 that came with your Mac (which may be called Software Restore, Additional Software & Apple Hardware Test, or Mac OS 9 Install Disc, depending on your Mac model).

Other requirements

Check the Read Before You Install file for more information that may be relevant to your particular setup. This file is included as a text document on the Mac OS X Install CDs (or DVD). The contents of the file are also presented when you run the Install utility.

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