2.5 GHz dual-core Intel Core i5 processor (Turbo Boost up to 3.1 GHz) with 3 MB shared L3 cache.

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Why won't my Mac start up after Sierra update?

I did not want to update to Sierra (Yosemite was running just fine) but Adobe Premiere refused to run without it.

Now the laptop will not startup. At first, I had a progress bar on the loading screen that stalled and continued stealing overnight. Now, it keeps attempting to boot up but not getting far.

Lots of code is on the screen. I'm not a programmer. Any idea what this means?

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Edit: pressing shift to enter safe mode does nothing. When pressing option, this screen comes up. But clicking anywhere just brings my right back to code startup screen.

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Answered! View the answer I have this problem too

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Edit: added image thank you Dan!


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First see if it will boot in Safe Mode by holding down the Shift key on boot.

Boot up to the repair partition by holding down the Option key on start up. Go to Disk Utilities and see if the Disk can be repaired. Try booting again. If it fails do a reinstall from the repair partition.

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The shift on start up does nothing, I already tried that. I tried option. It does bring up a different screen, one with a picture of Macintosh HD. There is only an up arrow to click on, but this brings me right back to the code on startup screen.


Yuck. We need to boot it from an external source. Either from your back-up drive (you do have a back-up drive? Or in Target Mode from another Mac and do a full reinstall and virus check.


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Hannah Jay will be eternally grateful.
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