|1||Disable extensions: Restart the computer while pressing the Shift key.||If the computer starts up without loading extensions, then you have a probable extension conflict. If not, go to Step 2.||System 7.5 through Mac OS 9.x, see technical document 30929 - "Mac OS: Extension Conflict Troubleshooting/Extensions Manager Features"
System 7.0 through System 7.1.x see the Troubleshooting Extensions section later in this document.
|2||Startup from Disk Tools: Restart the computer by starting up from the Disk Tools floppy disk or startup CD.||If the computer restarts from floppy disk or CD, you may have unusable system software or a hard drive issue; continue to Step 5. If not, go to Step 3.||See: Disk Tools.|
|3||Disconnect external devices: Disconnect all external devices (such as SCSI devices, USB devices, printers, network cables, extra monitors, and so on).||If the computer starts up with no external devices attached, you have a possible out-of-date driver or a SCSI ID or software conflict or USB issue. If not, go to Step 4.||See: Troubleshooting Peripherals|
|4||Reset PRAM: Press Command-Option-P-R during startup to zero out the information the computer maintains on ports, devices, Finder, and network settings.||If the computer starts up after resetting PRAM, then there was most likely corrupt information in the Parameter RAM on your computer. If not, go to Step 5.||See: What's in PRAM? (later in this document)|
|5||Update the hard disk driver software.||If the computer starts up after reinstalling the hard disk driver, then either the hard disk driver software was out of date, or unusable. If the computer still does not start up properly, go to Step 6.||Use either Apple HDSC Setup or Drive Setup to reinstall the hard disk driver software.|
|6||Perform a clean installation of system software: Follow the steps in the Knowledge Base to perform a clean installation of system software.||If the computer starts up after a clean installation, then one of the files in the System Folder was unusable. If not, go to Step 7.||Carefully go through the Previous System Software folder created during the clean installation; look for fonts, extensions, control panels that you might need. Move them back where they belong.|
|7||Other steps to try:
||If the computer starts up after trying these efforts, then you have successfully corrected the issue and are ready to work. If not, go to Step 8.||Make regular backups in case you have trouble again. (But do not destroy the backup you restored in this step.)|
|8||Last step:||If your computer still does not start up, there is most likely a hardware issue.||Contact your local Apple-authorized service provider to isolate and correct your issue.|
These actions, and the preceding procedures, may help you resolve a number of common issues, including unusable or missing files, extension incompatibilities, USB issues, or SCSI termination issues. If you have any third-party (non-Apple) devices or software, please adhere to the recommendations of the manufacturer if they differ from the more general instructions presented here.
Important: As a precaution, you should back up important files regularly to minimize the risk of data loss.
Extensions load into memory at system startup time, and actually change the way the operating system works. When they are incompatible with the version of the system software you run, or conflict with one another, they can cause unexpected results.
Extensions are sometimes also called INITs; they are usually in the Extensions Folder or the Control Panels folder within the System Folder. They may also be at the root level of the System Folder itself. As they load into memory at system startup time, their icons usually appear on the bottom of the screen.
To troubleshoot extensions, follow these steps:
- 1. Restart, and hold the Shift key down until you see the message "Welcome to Macintosh -- Extensions Off", then release the Shift key. If the issue goes away, then continue these steps to determine which extensions are causing the issue.
2. If you are running System 7.0 through 7.1.2:
1. Check your Extensions folder, your Control Panels folder, and the root level of your System Folder for non-Apple chooser and system extensions and control panels (such as virus protection, screen savers, compression utilities, and so on.).
2. Drag these outside of your System Folder (make a new folder for them named Disabled Extensions).
3. Restart. If the issue goes away, then you have succeeded in removing the issue extensions. Proceed to the step 4. Otherwise, check through your System Folder again for extensions you may have overlooked.
4. To determine which of the extensions you removed was causing the issue, drag the extensions one at a time onto the icon of your closed System Folder. The system puts them where they belong. Restart after each addition. When the issue returns, you will know that it is the last extension you dragged to the System Folder. Remove it and restart. Check its version number for compatibility. Try reinstalling from the original software, or contact the software vendor.
3. If you are using System 7.5 through Mac OS 9.x, see technical document 30929 - Mac OS: Extension Conflict Troubleshooting/Extensions Manager Features.
4. If you are still unable to resolve the issue, perform a clean installation. See technical document 30691 - "Mac OS: When and Why to Perform a Clean Installation"
Using Disk Tools
The Disk Tools Disk or Startup CD that comes with the system software includes a System Folder, Disk First Aid, and, depending on your version of system software, one of these utilities:
- Apple HD SC Setup
- Apple Internal HD Format
- Drive Setup
When you are having trouble starting up the Macintosh computer from the hard drive, first start up from the Disk Tools Disk or Startup CD. This way you can repair any issues on the hard drive (which you cannot do when it is the startup drive). The startup disk icon displays in the upper right corner, and the hard disk icon should display below it.
Disk First Aid
Use Disk First Aid to check the internal hard disk for directory issues. Simply launch Disk First Aid, highlight the drive icon for the applicable hard drive, and click Verify. (On older versions of Disk First Aid click Drive until the selected drive is your internal hard disk, then click Open and Start.) If Disk First Aid finds issues it cannot repair, you may want to try other third-party disk utilities to correct the issue. However, if you cannot repair the disk, you need to reformat it. Make sure you have a backup of your data before reformatting. If you don't have a backup, you may want to take your drive to a Service Provider that specializes in hard disk recovery.
Apple HD SC Setup
Apple HD SC Setup is a disk formatting utility for Apple hard disks. If you have a third-party hard disk in your Macintosh, you get the message that Drive Selection Failed when you launch Apple HD SC Setup. In this case, use the third-party disk formatting utility that came with your drive, or contact the vendor of the drive. To use Apple HD SC Setup on an Apple hard disk, launch the utility and click the Update button to reinstall the hard disk drivers. You can also use the Test button to test the hard disk, and Initialize to reformat.
Internal HD Format
This utility enables you to reformat an IDE hard drive found in Macintosh 630 series and Power Macintosh 5200/5300 series computers.
This utility enables you to test; partition; install hard disk drivers; and reformat SCSI hard drives, IDE hard drives and some third-party removable hard drives. Drive Setup only works on Power Macintosh computers or computers with a 68LC040 processor and an IDE hard drive.
Note: Initializing erases all data on your hard disk. Ensure you have a backup before doing this.
If you were experiencing issues that went away when you disconnected the peripherals, follow these guidelines:
If you have SCSI devices connected to your Macintosh, make sure that you have followed the vendor's instructions for installation. Specifically, check:
- Termination - SCSI chains should be terminated at the beginning and end of the SCSI chain. The internal hard disk (if any) is considered the beginning of the chain, and has terminating resistors. Whatever device is last in your chain should also be terminated. Check the manuals that came with the devices to discover if they are internally terminated. If not, the last device needs an external terminator. Devices in the middle of the chain should not be terminated. Again, check the manuals or contact the vendor.
- Unique SCSI ID - Each device on the SCSI chain requires a unique ID number between 0 and 7. ID 0 is generally used on internal hard disks; ID 7 is reserved for the Macintosh itself. If your computer has a built-in CD-ROM drive, it is usually set at SCSI ID 3. This leaves numbers 1,2,4,5, and 6, available to assign to your external devices. Consult the manuals that came with your devices to determine how to set their ID numbers.
- High-quality SCSI cables - Use high-quality cables, the shorter the better (three feet or less). When chaining more than one external SCSI device, try to use the same brand of cable.
- Starting up - External SCSI devices should be powered on, one at a time, before starting up the computer. When shutting down, shut down the Macintosh first. Once the Macintosh has powered down (the screen goes dark or you get a dialog box telling you that it is OK to turn the computer off) then turn off each device, if desired. Never connect or disconnect SCSI cables when any device is turned on. Do not start up the computer with a SCSI device turned off, unless the manufacturer specifically says in the manual that this is acceptable.
Universal Serial Bus (USB) Devices
If you are experiencing issues starting up when a USB device such as a mouse, keyboard, printer ,or drive is connected, first make sure the connections are snug. Then try another USB port, if the computer has more than one. If you are still having issues, contact the device vendor. Network Connections
If you have issues starting up with a network connector attached (such as a LocalTalk connector box), there may be issues on the network, or with the connector itself. First, swap out the connector with a known-good one; if issues persist, consult with your network administrator.
Apple Desktop Bus (ADB) Devices
If you are experiencing issues starting up when an ADB device, such as a mouse or keyboard, is connected, first make sure the connections are snug. Try another ADB port, if the computer has more than one. If you are still having issues, contact the device vendor.
What is in PRAM?
Parameter random-access memory (PRAM) is a small amount of memory continually powered by a lithium battery to retain its contents even when the computer is shut down. PRAM maintains information such as background color, default video selection, network information, serial port information, and default highlight color.
Even though you may not know what in PRAM is causing issues on your computer, resetting this information can often be an important troubleshooting step. This is particularly true when serial devices are connected to the computer, or when networking software is in use.
Resetting the PRAM resets your Macintosh computer to the factory defaults, so anything you have customized (like background or highlight color) is reset, the alert sound may be different, and AppleTalk will most likely be turned off. Use the control panels to set the computer back to the way it was before the PRAM was reset.