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djdunc Author

Level 1

4 points

iMac 2017 Catalina to big sur constant reboot

am trying to upgrade to Big Sur from Catalina (10.15.7) on a 2017 iMac 27" 5K

first tried to install in late January - i think i downloaded v11.1 - but was having the restart issue mentioned in the forums here, couldn't get it working so after a few hours finally gave up and using option on restart rebooted back into Catalina and then deleted the "install big sur" application from Applications folder. I tried resetting nvram, smc, ran disk utility and fixed disks, unplugged all peripherals etc

Yesterday i thought I would try again - this time downloaded 11.2.3 and tried to install but same problem - progress bar gets to about 20% and then just keeps rebooting (about every 5 minutes).

Before I erase the drive and try a completely fresh install is there anything else I can try? I have seen several posts here and elsewhere with people asking the same question but have not found any explantation of why this may be happening.

iMac, macOS 10.13

Posted on Mar 30, 2021 3:16 AM

Top-ranking reply

kaz-k

Level 9

50,238 points

Posted on Mar 30, 2021 11:18 AM

Hi,

Did you try safe mode boot then normal boot? Oh well it maybe doesn't work, though it's worth trying.

How to use safe mode on your Mac - Apple Support

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