Q: iMac freezes after upgrade to macOS Sierra

I called Apple support but you need to get to system preferences to find the option by holding down the command and R button simultaneously after you power up.

The issue being discussed here has nothing to do with "problem downloading Sierra". I was able to download Sierra just fine, and even installed it without incident on my MacBook Air. When the SAME download is installed on my 27" iMac, it installs without incident, and boots and run fine, but will eventually freeze up. I think we need to be careful not to dismiss this as corrupted download issue.

I've gone ahead and installed the beta. Will report as the problem arises.

FWIW, seems to have been stable the last few days, prior to moving to the beta, but I've been proactive about shutting down Safari when I don't use it.

m0pher

Having a similar issue on a newer model of iMac.  See my post from today titled, "Constant Freezing and Restarts - iMac (Retina 5K, 27-inch, Late 2014)" for the details of my symptoms and troubleshooting I've done with no luck in reaching a resolution.  Also, spent 4 hours with Apple Support reps and took my iMac into the Apple Store.  Apple determined there was no problem after running diagnostics for 24 hours.

Note, I had the issue under El Capitan and Yosemite, so doesn't appear downgrading is an option for my model.

Let me know if you find anything out, and I'll do the same here.

tomantrim

I have a 2009 iMac (C2D 3.06Ghz) with 12Gb RAM and exactly the same problem - freezing a few times a day when Safari is open, requiring hard restart. Very frustrating.

I know this does not help, but I am having the exact same issue as mOpher. Same symptoms, and it only happens when using Safari. iMac late 2009.

I have always just updated this machine with every new version of OSX. I will now try to do a clean install of Sierra. The machine is very slow after upgrading to Sierra

Update: I've installed a clean copy of the latest Sierra beta (10.12.1 beta 5), and unfortunately, the issue is still there. It locked up within a couple hours. I've submitted a new bug report via the Feedback Assistant provided with the beta.

Similar status here. I've installed beta 5 (not clean...) and the pace of crashes has slowed, but they're still happening. I report them as they happen -- we'll see what comes of it.