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This chapter is from the book

The Classic Environment

The Classic environment is a complete implementation of Mac OS 9.x on top of Mac OS X. To Mac OS X, Classic is nothing but another application; to a user, however, Classic is a gateway to his older software programs.


You must have at least 128MB of memory to use Classic, an installed copy of Mac OS 9.x, and a 400MHz G3 (or faster) is recommended. Because Mac OS 9.x no longer comes with Mac OS X, you must order it from Apple.

Classic is a process under Mac OS X. Mac OS X must be running for Classic to work. In essence, you're booting two operating systems simultaneously.

When using the Classic environment, the 9.x operating system must access all hardware through the Mac OS X kernel. This means that software that accesses hardware directly will likely fail. Users of 3Dfx video cards, hardware DVD playback, video capture cards, and even some CD writers will find that their hardware no longer functions correctly.

On the other hand, Classic brings the benefit of Mac OS X's virtual memory underpinnings to legacy applications. Each Mac OS 9.x application can be configured for a much larger memory partition than was possible previously. To the Classic environment, the virtual memory appears to be real memory. Programs have much more breathing room in which to function.

Working with the Classic environment is a somewhat unusual experience. Depending on the application running, there can be graphic anomalies and confusing filesystem navigation. This chapter shows what you'll see and what to do when things don't seem to work right.

Launching Classic

The Classic environment is typically launched once during a Mac OS X login session—either manually or automatically. After it is running, Classic remains active until you log out or manually force it to shut down.


Classic does not gain all the stability features of Mac OS X, such as protected memory. If an application crashes in Classic, it can bring down all applications running in Classic. The Mac OS X system will be unaffected, but you might need to manually restart the Classic environment.

There are two ways to launch the Classic environment: by double-clicking a Classic application and through the Classic pane within System Preferences.

Classic applications appear to the Mac OS X Finder just like any other application. To verify that a piece of software is indeed a Classic application, you can select the icon and choose File, Get Info or choose Get Info from the contextual or action menus. Figure 3.63 shows the General Information pane for the Graphing Calculator, a Classic application.

Figure 3.63Figure 3.63 The General Information pane identifies Classic applications.

Memory Settings

Classic applications, because they still use the Mac OS 9.x Memory Manager, require a preferred and minimum memory size to be set. Because you have no direct access to the 9.2 Finder under OS X, Classic applications have an additional Get Info pane called Memory, as shown in Figure 3.64.

Figure 3.64Figure 3.64 Classic applications allow memory limits to be set.

Two limits can be set:

  • Minimum Size—The minimum amount of memory that an application must have to run. The Mac OS 9.x environment prohibits the application from launching unless the minimum memory size can be met.

  • Preferred Size—The amount of memory that you want the application to have. This is the upper limit of the memory partition that will be requested from Mac OS 9.x.

To take advantage of the new Mac OS X memory architecture, set these values higher than you would in older versions of the Mac OS. If you do, be aware that your settings here will carry over if you boot directly into Mac OS 9.x, where you might not have as much real or virtual memory available.

Forcing Carbon Applications into Classic

Carbon applications are a special case of Mac OS X application. They are capable of running natively on Mac OS X, and on Mac OS 9.x through the use of CarbonLib. If you want to use the Classic environment to launch a Carbon application, a setting within the General pane of the Get Info pane can force a Carbon-compliant package to launch through Classic.

To launch a Carbon application in Classic, check the Open in the Classic Environment check box and then close the info pane. Double-clicking the application launches it in Classic rather than in Mac OS X until the box is manually unchecked.

Configuring Classic

If you have multiple Mac OS 9.x installations, or want to manually start or stop the Classic environment, you can do so from the Classic System Preferences pane. First, open System Preferences (path: /Applications/System Preferences) and then click the Classic icon.


The Classic Preferences pane can control how and when Classic boots. As shown in Figure 3.65, the following options are found in the Start/Stop pane of the Classic pane:

  • Select a Startup Volume for Classic—Mac OS X can start the Classic environment by booting any available Mac OS 9.x system. It is recommended that you use a separate drive or partition for Mac OS 9.x, as you will be able to boot to the Mac OS 9 partition, bypassing Mac OS X in case of an emergency.

  • Start Classic When You Log In—If you want Classic to start up immediately after you log in to your computer (or immediately at startup, if you're using Mac OS X as a single-user system), click this button. Be warned; the Classic environment takes a few minutes to start, and your system performance will be degraded during this time.

  • Hide Classic While Starting—The Classic startup window will be hidden while the Classic environment boots.

  • Warn Before Starting Classic—Use this option to force Mac OS X to prompt you each time it launches the Classic environment. If you find yourself accidentally starting Classic by double-clicking legacy files, and so on, this can be helpful.

  • Show Classic Status in Menu Bar—Adds a menu extra, shown in Figure 3.66, that can start and stop Classic and provides access to the Classic Apple menu items.

  • Start/Stop—Click the Start button to launch Classic manually or Stop to shut it down.

  • Restart—Is equivalent to choosing Restart from the Mac OS 9.x Finder. Open applications prompt you to save open documents and then exit. The Classic environment will reboot.

  • Force Quit—If Classic becomes unresponsive (that is, it crashes), the only option is to force it to quit. Open documents are lost, exactly as if Mac OS 9.x crashed (as it tends to do from time to time). You can also use the Control-Option-Escape keystroke to force it to quit.

Figure 3.65Figure 3.65 The Classic System Preferences pane configures the startup volume and allows manual startup and shutdown.

Figure 3.66Figure 3.66 The Classic menu extra provides feedback on the status of Classic as well as provides controls for stopping/starting and restarting the environment.

Advanced Settings

Use the advanced startup options to provide control over the boot sequence and basic Classic operation. Figure 3.67 shows this pane.

Figure 3.67Figure 3.67 Advanced settings control the boot and runtime features of Classic.

You can make four modifications to the startup process:

  • Turn Off Extensions—Turning off the extensions is the equivalent of pressing Shift while booting into Mac OS 8 or 9. This prohibits additional control panels and extensions—beyond those needed by the 9.2 operating system—from loading.

  • Open Extensions Manager—This opens the Mac OS 9.x Extensions Manager control panel during the boot process, allowing you to disable extensions that appear to be causing system instability.

  • Use Key Combination—This unusual option enables the user to choose up to five keys that will be kept in pressed state while Classic boots. Some extensions can be individually disabled by certain keystrokes; this feature lets you target those processes.

  • Use Mac OS 9 Preferences from Your Home—If selected, Classic maintains a separate set of preferences for your account. If unchecked, a systemwide preferences location is used.

After choosing your startup options, click the Start or Restart button to implement the selection.


The first time you boot Classic, the advanced options will not be available. Subsequent executions will enable all the advanced features.

Apple has also kindly included two features in the Advanced pane that help fix a common problem and speed up overall system functions—the ability to rebuild the desktop and put Classic to sleep if it is inactive:

  • Put Classic to Sleep When It Is Inactive For—When Classic is running, it is using your system resources. The Classic environment continues to use CPU time even if you aren't running a Classic application. This is because Mac OS 9.x must keep up the basic system maintenance and monitoring processes that happen behind the scenes. If you choose to put Classic to sleep, it stops using these resources after the length of time you choose.

  • Rebuild Desktop—Rebuilding the Mac OS 9.x desktop can help solve "generic icon" problems (files that should have custom icons show up as generic white icons in the Finder), as well as issues with documents that can't find the appropriate Classic application to open them. If your Classic environment starts to act in unusual ways, rebuilding the desktop is a good place to start.


Classic functions best when it is used as a means of accessing legacy applications and data. You should maintain as minimal a system software installation as possible. Extensions and control panels that are not needed should be removed. If possible, use the Open Extensions Manager startup option to choose one of the base extension sets from within the Extensions Manager and stick with it.


With Classic running, the Memory/Versions pane displays the processes that are active and how much memory they are consuming, as shown in Figure 3.68.

Figure 3.68Figure 3.68 The Memory/Versions pane gives feedback on active Classic processes.

To display information about background Classic processes, click the Show Background Processes check box. Information about the version of Classic and its supporting software is displayed at the bottom of the pane.

Direct Booting Mac OS 9.x

To boot directly into Mac OS 9.x, use the Startup Disk System Preferences pane, shown in Figure 3.69.

After searching the mounted disks (this can take a while) for viable systems, each of the accessible system folders is listed in the Startup Disk pane. Each icon lists the OS version and volume name. To select one, click the icon; a status message appears at the bottom of the screen describing your choice.

Figure 3.69Figure 3.69 Boot directly into Mac OS 9.x using the Startup Disk pane.

Quit the System Preferences application when you're finished or click Restart. The next time your computer boots, it boots into the operating system you selected.

Booting into OS X

To switch back to OS X after running 9.2, you follow a similar process as switching from Mac OS X to Mac OS 9. From the Apple menu, choose Control Panels; then select and open the Startup Disk control panel.

Each mounted disk is displayed on a line in the control panel. Disks that include a bootable system folder have a disclosure arrow directly in front of them. Clicking the disclosure arrow displays the operating systems located on that disk, along with their path and version.

To boot into OS X, highlight the OS X installation within the list and then click the Restart button in the lower-right corner. If you don't want to restart immediately, close the control panel. The next time the system restarts, it boots into the selected system.


Advanced users may want to use the bless command, which chooses what folders can (and should) boot your computer. In short, on a two-partition system, bless can be invoked like this to set your Mac's OpenFirmware to boot from OS 9:

sudo /usr/sbin/bless/ -folder9 '/Volumes/<path to Mac OS 9 System Folder>' -setOF

Or, from Mac OS X:

sudo /usr/sbin/bless/ -folder '/System/Library/CoreServices' -setOF

Familiarize yourself with the command line (see Chapter 12) and read the bless man page before attempting to use the command.


One final alternative means of choosing your startup devices is to hold down Option when restarting your computer. The boot manager built into your Macintosh firmware will load, displaying all recognized boot devices.

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