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TOPIC
Certain combinations of Apple installers can cause the Mac OS ROM file to be downgraded to an earlier version. Since specific Mac OS ROM versions are meant for specific releases of Mac OS, mismatching these components can cause unpredictable behavior. Depending on the Mac OS version and the ROM version which are mismatched, symptoms can vary from an unnoticeable difference in operation to the computer not responding during the startup process.
DISCUSSION
- iMac
- Power Macintosh G3 (Blue and White)
- PowerBook G3 Series (Bronze keyboard)
- Later computers (computers which use a software-based ROM file)
Affected Products
The resulting symptom is a computer that stops responding during the startup process after the "happy Macintosh" icon appears.
Running iMac Update 1.0
iMac update 1.0 is intended for use only on iMac computers running Mac OS 8.1. Running this update on a computer using Mac OS 8.5 or higher causes the Mac OS ROM file to be downgraded. The Mac OS ROM file included in this update does not work correctly with other versions of system software and causes the computer to stop responding during the startup sequence when improperly applied.
Note: iMac Update 1.0 is no longer available from Apple Software Updates sites.
Custom Installing OS Components
Running an OS installer from the system CD that shipped with some Macintosh computers has the potential to downgrade the Mac OS ROM file if the existing OS on the computer is more current.
Correcting The Issue
If you have inadvertently replaced your Mac OS ROM file with the incorrect version in either of these scenarios, you can replace it and repair the System Folder by running the appropriate Mac OS installer. Follow these steps:
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1. Start up from the most current Mac OS CD you have.
2. Locate the System Folder on the hard drive.
3. Open the System Folder and locate the Finder.
4. Select the Finder file and choose Get Info from the File menu.
5. In the Info window, look just below the word Finder at the top of the window to see what version of the OS this System Folder is currently running. See Figure 1.
6. Run the OS installer or updater that matches this version to replace the Mac OS ROM file with the correct, matching version.
Figure 1 Info window for the Finder; Mac OS 8.6 is running.
If you are running an iMac with Mac OS 8.6 for example, and you installed Mac OS 8.6 by running the 8.6 updater, simply start up from any bootable CD and run the 8.6 updater again. You can run it either from a Mac OS 8.6 update CD (this update CD is bootable) or from the hard drive if you have downloaded the update from the Internet.
If Mac OS 8.5 is installed on the hard drive, run the Mac OS 8.5 installer. In this case, you do not have to reinstall all components such as ColorSync and Speech Recognition. To save time, choose the customize option in the installer and check to install only Mac OS 8.5.
For additional information on which ROM version goes with which OS version, see the following Knowledge Base article:
Article 24965: "
Mac OS: Matching Mac OS ROM File To Mac OS Version
"