The Boot Process
Mac OS X requires 9.1 or later to be installed in order to boot Classic. If you are running an earlier version, you must upgrade it first. The first time that Mac OS X boots the Classic environment, it must add additional software to your computer to be able to operate, demonstrated in Figure 4.5. This software acts as a bridge between the Mac OS X process monitors and I/O systems. If you choose not to add these components when prompted, Classic will exit.
If you have a Mac OS Xcompatible version of Mac OS 9.x that is not the most current release, Mac OS X might give you a warning with instructions on how to update the earlier operating system.
Although Mac OS 9.2 is the preferred Classic OS for Mac OS X 10.2, users with 9.1 will still be able to boot into Classic and upgrade at their leisure.
As Classic boots, it will load all the extensions and control panels that you had previously installed on your Mac OS 9.x installation, as shown in Figure 4.6. If you installed Mac OS X from scratch, you should be in good shape. If you're upgrading an older system, you might find that some extensions cause Classic to crash.Figure 4.6 Classic loads your extensions as it boots.
Extensions or control panels that access hardware and those that patch the Mac OS system routines are most likely to cause problems under Classic. In some cases, they may interfere with the booting process altogether.
So, what do you do when Classic won't boot?
There are two avenues for resolving a problem with Classic. The first is to use the Mac OS X Classic System Preferences panel to disable extensions during startup. Although your initial reaction might be to hold down the Shift key while Classic starts, this will not work. The Classic boot window does not pass keystrokes directly to the booting Mac OS 9.x system.
Instead, you can use the advanced startup options to provide some control over the boot sequence. Open the System Preferences and choose the Classic panel. Click the Advanced tab to see the advanced startup options. Figure 4.7 shows this panel.
You can make three modifications to the startup process:
Figure 4.7 The Classic Advanced options provide some control over the startup sequence.
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. The Mac OS 9.x Extensions Manager will be discussed shortly.
Use Key Combination--The Key Combination option is unusual; it 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.
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.
Mac OS 9.x Extensions Manager
If you have no idea what is causing your system problems, your best choice is to open the Extensions Manager. This will let you start with a base set of extensions and build them back up into a working system.
A few seconds into the boot process, the Extensions Manager will appear in the OS X Classic boot screen. The Extensions Manager is shown in Figure 4.8.
The Extensions Manager consists of a window that lists all the extensions, control panels, and startup items on the computer. To disable an item, toggle the On/Off check box to the Off state. Many extensions contain packaging information (what program installed them), as well as a description of their purpose.
Click the Show/Hide Item Information disclosure arrow to display extended information about any selected item.Figure 4.8 The Extensions Manager helps you find a base set of extensions that will let Classic boot successfully.
Choosing a Base Extension Set
The easiest way to get yourself to a working 9.2 installation is to use one of the two built-in sets from the Selected Set menu at the top of the window:
Mac OS 9.x Base--The Base set includes only the basic components needed to boot 9.2. Components such as speech synthesis are not enabled.
Mac OS 9.x All--All the extensions included in Mac OS 9.x are active.
After selecting a base set, quit out of the Extensions Manager and allow the Classic environment to boot. Within a few minutes, Classic should be active. If you have no need for the extensions you've disabled, you're done. On the other hand, many applications rely on extensions to be able to function. Most Mac users are adept at fixing extension conflicts, but in case you're new to the task, the process goes a bit like this:
Starting with a working base set, add all extensions related to a package back to the system. You will be prompted to create a new extension set if you're using one of the built-in sets.
Restart the system with the new set.
If the startup fails, the fault lies in the recently added extensions. Disable them, add the remaining extensions back to the system, and restart.
If the startup succeeds, go to step 1 and repeat.
Seasoned users might find that this process is faster if they simply remove the extensions from the Mac OS 9.x System Folder manually.
Just because you start with a working system does not mean that Classic software added after installation will not break something. Mac OS X does not control access to the OS 9.x System Folder.
If Classic doesn't boot even if you are using a base extension set, there might be problems with the system disk itself. You can learn how to repair common disk problems using the Mac OS X Disk Utility in Chapter 5, "Applications and Utilities."