Sleeping is fatal for my iMac
Since upgrading my iMac from Mavericks to 10.10.3, it crashes every time it sleeps. It’s difficult to wake, needing several goes with the power button, and I get the kernel panic message. I enabled ‘Prevent computer from sleeping automatically when the display is off’ in System Preferences and this has (temporarily?) fixed the problem. Any advice on a proper fix for this? Ken Shifrin The crash is probably happening when the iMac wakes up, rather than when it goes to sleep. If you get as far as a cursor on a black screen, this may be caused by an automatic update that hasn’t finished. Press the power button for 10 seconds, then restart with ß held down until you see the Apple logo. Once the cursor appears, enter your username’s first letter (if you have more than one account), type your password blind and hit ® . This should get you past the login screen, so the update can complete.
If you don’t even see the cursor, it’s more likely a RAM fault. I’ve seen three Macs refuse to wake from sleep since upgrading to Yosemite, and all were restored to life with new RAM. Use the Advisor tool at http://uk.crucial.com to find the right kind. Rather than play musical chairs with the old modules, I advise replacing all of them.
If your Mac crashes when it wakes from sleep, it’s better to find out why than turn off sleep mode.