Upgrading to Apple's Snow Leopard OS: What you need to know

With a spiffy new installer, the Mac OS X upgrade process is quicker and easier than ever

In building Snow Leopard, the latest version of Mac OS X (version 10.6), Apple focused more on under-the-hood improvements to boost speed and stability than on adding new features. That contrasts with its predecessor, Leopard (Mac OS X 10.5), which added more than 300 new features when it was released two years ago.

In Snow Leopard, Apple focused on making the OS run faster using technologies like Grand Central Dispatch (which allows a Mac with a multi-core processor to more effectively distribute work among cores) and OpenCL (which allows a Mac's graphics processors to be used for general computing tasks whenever possible), and making all the core system applications and most core components 64-bit.

But before you can appreciate Snow Leopard's performance, user interface refinements, and technology tweaks, you have to get it installed. Here's what you need to know about the upgrade process -- which in itself illustrates both UI improvements and under-the-hood advances over past versions of Mac OS X.

Can you run Snow Leopard?

The most important question to answer before upgrading to Snow Leopard is whether your Mac can handle it. First, you'll need an Intel-based Mac. (Not sure what you have? Click the Apple menu and choose About This Mac. If your processor is a PowerPC, you're out of luck; if it's from Intel, you're good to go.)

Any Intel Mac will run Snow Leopard, provided it has at least 1GB of RAM (though 2GB or more will deliver better performance) and 5GB of hard drive space. You'll also need a DVD drive for installation. (MacBook Air owners can use a DVD drive in another computer, provided they turn on CD/DVD sharing.)

It's worth noting that not all Intel Macs can make use of 64-bit processing. That's because not all Intel Macs have 64-bit processors.

The first Intel Macs shipped with either an Intel Core Duo or Core Solo chip, both of them 32-bit processors. Apple switched to the Core 2 Duo processor, which is 64-bit, across most of its product lines pretty quickly. You can check your processor model using About This Mac.

With an Intel Core 2 Duo processor and 2GB of RAM, this iMac -- still running Mac OS X 10.4 "Tiger" -- can take advantage of Snow Leopard's 64-bit processing.

This doesn't mean that early Intel Macs won't see improvements with Snow Leopard -- they will -- but they may not see as big a performance boost as newer Macs.

Any Mac users still running Tiger (Mac OS X 10.4) can upgrade directly to Snow Leopard, skipping its predecessor, by purchasing Apple's Mac Box Set, which includes Snow Leopard and the latest versions of iLife and iWork for $169. This ensures that your Mac will be able to run all the Apple tools as well as Snow Leopard.

Important: Before you upgrade, back up

Before you even think about installing the new operating system, be sure to perform a full backup of your system.

With Snow Leopard, Apple has made the installation process cleaner and more reliable than ever; the installer can even finish an installation properly if your Mac is unexpectedly powered off during the process. Nevertheless, a good backup is always prudent. If you've been using Time Machine in Leopard, you've probably got one already.

In-place upgrade vs. clean install

With a major OS release, there's always the question of whether to perform a simple upgrade (where your files, applications, and system configuration files are left in place) or a clean install (where the target drive is backed up and erased before installation).

In the past, I, like many power users, advocated for a clean install -- it can help avoid conflicts between older applications and the new OS or any damaged configuration files. It can be a good troubleshooting step if you can't find the source of ongoing problems or if you have damaged system files. But the snazzy new installer for Snow Leopard (more on that in a minute) detects potential issues, making a simple in-place upgrade not only sufficient, but the better and easier way to go.

The main advantage to a clean install is from a personal housekeeping perspective. Since most computers over time collect files that are no longer needed -- anything from old to-do lists to applications you installed but never use -- a clean install forces you to take a look at what's on your computer and do some spring cleaning. Given that it means copying files, erasing the disk, restoring and organizing your files, and resetting all of your preferences and system settings, a full-fledged clean installation it isn't worth the hassle. Just find some time to go through your hard drive and clean it out.

If you do perform a clean install, you'll need to boot your computer using the Install DVD by restarting the computer while holding down the C key. Then use Disk Utility (located in the Utilities menu in the menu bar after you've booted from the Install DVD) to select your hard drive and erase it. Quit Disk Utility to return to the installer and proceed with your installation as outlined below. Be forewarned: Starting up from the installation disc and erasing your hard drive for a clean install will make the entire installation process take longer.

Longtime Mac users are probably familiar with the old "Erase and Install" (which erased the contents of the hard drive before installing the new OS) and "Archive and Install" (which retained a copy of all system files for later retrieval) options for installing Mac OS X. Although you can still erase your hard drive for a clean install using the steps outlined above, these two options are no longer part of the actual installation process.

Meet the Mac's new installer

When you put the Snow Leopard Install DVD in your Mac, the Finder window that opens looks pretty much like that of any Mac OS X installation disc (the obvious exception being the Snow Leopard icon).

But the second you double-click the installer, you'll notice something's different. Instead of being asked to restart your Mac and boot from the Install disc, you'll see a screen with two options: Utilities and Continue. That's because you don't need to boot from the DVD to install Snow Leopard (though you can do so later down the road if your Mac has problems or if you want to erase your hard drive before selling your computer, for instance).

The reason your Mac doesn't need to boot from the Install DVD is because one of the first things the installer does is copy all the files you'll need for installation to your hard drive. This has a few important benefits. First, it saves you time because you don't have to wait for your Mac to boot from the DVD (which often takes a few minutes or longer), and the installation itself goes more quickly because the files are being installed from your hard drive.

It also means that when the Mac checks the integrity of the files to be installed (which used to mean verifying the integrity of the DVD, a process that took so long most people opted to cancel it), it does so after the files have been copied to your hard drive, speeding up the process but also making integrity checks a built-in part of the installation (since you can't skip them).

The Snow Leopard installer has a couple of other tricks up its sleeve. Before installation, it scans your Mac for any applications or other tools that extend Mac OS X (like third-party System Preferences panes or device drivers) that are known to cause problems with Snow Leopard. The installer doesn't delete them, but it does move them out of any system folders or directories to ensure a smooth installation.

The installer also has a safe redo feature. If something interrupts the process (say you unplug your iMac by mistake), that's not a problem for Snow Leopard. With the installation files actually on your Mac's hard drive and the fact that every part of the install is written to a log file, the installer can simply pick up where it left off when your Mac is restarted.

Now, back to that initial installation screen: The Utilities option lets you restart and boot the computer from the Install DVD (the same as if you held down the C key during a restart) in case you want to erase or repair your hard drive, or restore it from a Time Machine backup. If you're doing a simple upgrade to Snow Leopard, click the Continue button.

Streamlined installation

In addition to skipping the initial restart used in earlier installations, Apple has pared down the number of clicks it takes to install Snow Leopard. After you click Continue, the installer automatically selects your startup drive (the one that your Mac booted from). Many people only have one internal hard drive or partition, but if you have multiple drives or partitions, you can choose another drive; just click the Show All Disks button and make your selection.

Unless you want to customize the installation (more on that in a moment), click the Install button now. You'll be asked to confirm that you want to proceed and asked to provide your admin username and password. After that, take a break; there's no more user interaction required. (The computer will restart itself during the installation process without any input from you.)

The whole installation process typically takes 30 to 40 minutes, although it varies depending on your hardware and your installation choices -- I've seen some installations finish in notably shorter and longer time spans.

When you come back, your Mac will be running Snow Leopard. When you first log in using the new OS, the Setup Assistant plays the standard Mac OS X welcome video. If you've done an upgrade rather than a clean install, there is nothing to set up and you can close the Setup Assistant window after the movie plays. If you did a clean install, you'll need to provide registration details, and then the Setup Assistant will guide you through the basic setup and configuration steps. You're on your way.

Customizing the installation

Of course, you can customize the installation if you want to. Before clicking the Install button, click the Customize button to see the screen shown farther down the page.

As with previous Mac OS X installers, you can opt out of language translation packs and additional fonts for languages that don't use the Roman alphabet (like Cyrillic, Chinese, or Arabic) to save a bit of hard-drive space.

You can also choose which printer drivers to install, though this really isn't needed: The installer automatically looks for printers connected to your Mac or on your local network and installs only the drivers for those printers, saving a lot of space in the process. If you later connect a different printer, Snow Leopard will automatically download the appropriate driver when it's connected without any action on your part -- the complete plug-and-play dream, finally realized.

If you want to run applications that use the Unix X11 interface, you can choose to install X11. It's selected by default; if you don't want, deselect it.

Another option is to install Rosetta, the software emulator that Apple created so Intel Macs could run software designed to run on PowerPC-based Macs. For most people, leaving Rosetta out (that's the default) should be fine. Apple began the transition to Intel processors more than three and half years ago, so unless you have an app that hasn't been updated since sometime in 2006 you really don't need Rosetta.

You also have the option of installing QuickTime 7. Snow Leopard features a new version of QuickTime (the system files and applications that support multimedia playback) called QuickTime X. QuickTime X offers much improved performance, a very clean, minimalist interface, and new video streaming capabilities. Some older media formats might still require the older version of QuickTime, which is why Apple offers it, but most people won't need it.

Once you've made all your customization selections, click the Install button and proceed as outlined above.

After the installation

After finishing the installation, you're ready to start exploring Snow Leopard. A few of the things you'll notice immediately:

* Better overall performance, even in basic tasks like navigating the Finder, which has been rewritten

* An improved implementation of Stacks that allows you to browse hierarchies of folders from within a stack

* Preview icons in the Finder that actually do live previews, meaning you can click through pages of a document or play a video file in its icon

* QuickTime X's interface and ability to record and trim video using your iSight camera

* Smarter text selection and annotation features in Preview, Apple's tool for viewing and working with PDFs, which also now sports the ability to directly scan documents and create PDFs of them

Over the next few days, Computerworld will have more on Snow Leopard, including details about the differences between 64-bit and 32-bit computing and our performance tests comparing Leopard to Snow Leopard on various Mac models.

Ryan Faas is a frequent Computerworld contributor specializing in Mac and multiplatform network issues. His newest book, iPhone for Work: Increasing Productivity for Busy Professionals, will be available from Apress this fall.

This story, "Upgrading to Apple's Snow Leopard OS: What you need to know" was originally published by Computerworld.

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