Macintosh iMac Boot Issues

• Gray Screen Startup
• Mac Stalls on Gray Screen

The problem is characterized by the display changing from the blue screen that occurs at power up to a gray screen (or black on more recent models) and delayed or froze on said screen.

possible culprit: bad device or peripheral

Disconnect all external peripherals, and keep them removed for the duration of these steps unless otherwise noted.

1. Turn off your Mac by pressing and holding the power button to force it down.
2. Make sure you remove the Ethernet cable, audio in/out cables, headphones, and any other peripherals.
3. Restore power, turn the Mac back on again

Now you can connect things one at a time and reboot to determine which hardware via process of elimination

System settings (BIOS Equivalent) reset

Mac doesn't use BIOS / CMOS like the PC even though Mac now uses the same processor family. They call it PRAM. The differences between BIOS Versus PRAM can be read about while the functionality is only relevant on this case because we want to reset these settings. Resetting the PRAM and the SMC returns your Mac's hardware to its default settings.

To reset PRAM:

1. Immediately press and hold the following keys: command+option+P+R. Continue to hold down the four keys for a long duration while the Mac resets them and then reboots.
2. Do not release keys until you hear the second startup chime.

You can also reset from the command prompt (this process is like the Cisco family of routers)

1. From console type

nvram ​-c

To reset System Management Controller:

• resetting a Mac's SMC depends on the type of Mac

1. Power off the Mac
2. Press and hold the power button for 10 seconds. Release the power button and wait a few seconds. Press the power button again to turn on the Mac.

Or you might have to open the mac up (remove cover) and do this...

1. Turn off Mac, unplug, then pop the top and look for a small button that reads SMC under the Drive 4 sled near top PCI-e slot.
2. Press and hold this button for 10 - 20 seconds.
3. Plug the mac back into AC power, wait 30 seconds, then power on

howto: safe boot

1. Shut down your Mac.
2. Press and hold the shift key.
3. Start up your Mac.
4. Release the shift key once you see the login window or the desktop.

howto: repair the startup drive

internal drive recovery partition

1. Turn on the Mac by pressing Command+R

alternative bootable medium such as an install disk or system startup disk which can be CD media or flash media.

1. Turn on the Mac and hold the C key.

operating system and system restore