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Bit of an odd one - upgraded to Mac OS Sierra, all working fine. When I shut the iMac down, the whole screen displays weird artefacts - (graphics glitch?), then shuts down fine. So not causing a problem, per se, but wondered if anyone else has had this issue?
iMac (Retina 5K, 27-inch, Late 2015), macOS Sierra (10.12)
I have similar issue too on a new 27" inch 5K retina 2TB imac. Thin vertical lines appearing in Time Machine.
Specs
I use the 2TB Time Capsule.On the first imac I did a comp'ete TM restoration. On the second imac I transferred the files from my old imac using Migration Assistance via ethernet.The lines do not appear in El Capitan only Sierra. I also get an array of multicoloured pixels on shut down from time to time. I have tried two different identically spec'd (is that a word?) imacs.I have tried the following with no success:
I suspect the problem lies with the GPU and Sierra.
Apologies, I have this exact problem (artefacts, multi coloured pixels on shutdown from time to time) plus the vertical lines in Time Machine described in my previous post.
Yes and he lines in Time Machine too! I noticed that a while ago and forgot. The multicoloured screen came back again last night.
Is it easy to go back to El Capitan then?
Yes, if your machine came loaded with El Capitan you will be able to reinstall it using Internet Recovery. Make sure you back up your data first. Read this link About macOS Recovery - Apple Support
I have this issue since update to Sierra and forward on my late '15 27. Clearly it is a software issue since it did not happen prior to Sierra and further builds. Also since it happens only on sporadic shutdowns. Could be any number of combination of things. Anyone have this on a clean install of Sierra? (if it only happens on shutdown ots probably harmless and I wouldn't bother reverting to El Capitan)
I rolled back to el Capitan and after 6 Shut Down no funny coloured lines yet.
Not rolled back, think I'm holding out for a fix until I do. However after going a good few days without seeing it, I've recently seen it more often than not. This 'appears' to be after using Chrome and when viewing the Time Machine windows (where you scroll back over days) - the latter has also been noted as having graphics glitches in itself, with faint black horizontal and vertical lines.
Tonight I shut down after using MS Excel and the screen went black, followed by a multicoloured, mainly pink, image of the spreadsheet I was working in!
Clean install of Sierra did not help me. Do you have fusion drive?
Mine is a solid state drive with the top end vid card for the '15.. Only happens on occasion during shutdown. If it happens on a clean install then not likely a third party kext I guess.
I was having the same problem with my new 27" 2015 iMac. When I restored my new iMac from my old, early 2009 iMac with Time Machine, it installed color profiles that were on that old machine. Used the ColorSync repair app and found 4 files that were bad. They were from my old iMac. Went into "library/color profiles" and found and deleted them. Problem Gone!
Just an update. After roll back to El Capitan no artifacts for 2 Weeks until upgrade to Sierra again and artifacts reappeared from time to time. Patricks Colour Sync tip did not find a issue. Otherwise no other problems with iMac.
Update
I first reported about this issue Nov 5.
Meanwhile I changed nothing on my hardware ( iMac , Retina 5K, 27-inch, Late 2015 , 4 GHz Intel Core i7 , 32 GB 1867 MHz DDR3 , AMD Radeon R9 M395X 4096 MB , 1 TB Flash Storage ) and software (Sierra 10.12.1)
... because :
I remember from a 'bluetooth issue' March this year ("bluetooth disabled after el capitan 10.11.4 update") with my iMac , with a lost connection of keyboard , and trackpad at startup .... that if it is up to Apple Help .. they let you try anything , taking a lot of time , and even for some impatient customers replacing their Mac ) - so now I am just waiting for Apple to fix this in next update of Sierra .. and , I recently read somewhere Apple will ...
I start and shutdown daily my Mac , and after Nov 5 the issue was not seen again ... until 2 or 3 days ago once more again (for now)
Hi Chael, same happens to me (same iMac model as yours but with 16GB, sierra 10.12.1). Occurred randomly twice last week. I thought it had something to do with heavy usage (I did some stuff with final cut pro, garage band, Photoshop and iTunes) but this morning it happened again after a simple cold boot, login, opened up Mail.app, printed one mail, did shutdown. Quite sinister to be honest.
I have the same issue occurring on a clean install of a brand new late 2005 iMac 27" I bought two weeks ago. This is using m395x with 4GB graphics memory and 16GB ram if that bit is of any help. The only way I was able to remedy the problem was to physically unhook the mac from electric outlet for a bit and starting it back up.
Was the clean install a Sierra install?
You may find that it goes and comes back randomly.
I'm tempted to do a clean install of El Capitan as I believe it's a driver issue. However I am starting to read about late 2015 iMacs 27 inch 5k being repaired because of this and it could be a power related issue, which doesn't sound great.
iMac 27" 5K Late 2015 screen artefacts on shutdown
