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When I turn my mac on (MacOSX High Sierra), the progress bar reaches 2\3, then the screen turns black again. This may repeat two or three times before it starts normally. What may be the cause of such strange behavior?
After clearing the entire cache via the console, the mac became boot normally.
Victor VosMottor thanks Monica
Posted 2019-12-31T16:26:00.473
Reputation: 81
0
When you Mac is booting it’s running a bunch of tasks. One of the cache related tasks may have been slowing the overall boot up performance. The process which changes the screen configuration I.e. color profiles were probably running simultaneously and it was slow enough for you to see it. You can always boot up holding command +V to boot up in verbose mode to see more information out your boot up process.
Theologin
Posted 2019-12-31T16:26:00.473
Reputation: 121
You don't mean it reboots, just that the progress bar vanishes then reappears? I think that's fairly normal. All mine do it, except they're older so are on grey not black, so it's perhaps more obvious that 'nothing went dark/broken'. I think it may be a part of getting all the graphics drivers loaded & figuring out how many screens are attached, etc. My 2nd screen remains 'off' until about the 2nd of those blank spots, then I see both screens, cursor appears & colour profiles switch on correctly, then a few seconds later, the desktop becomes visible [I have auto-login]. – Tetsujin – 2019-12-31T16:33:25.273
@Tetsujin No, it seems that it reboots, not just the progress bar vanishes and reappears. – Victor VosMottor thanks Monica – 2019-12-31T17:47:53.057
Ah… in which case, you need to start from the top - safe boot; make a new admin user; hardware test, etc. Long process of elimination... – Tetsujin – 2019-12-31T17:49:16.630