Hi,
TL;DR
Please watch the video and comment on your own experiences with similar outcome. Thanks.
Link to video on my Droplr account: http://d.pr/v/Faqf
Continued ...
Here's some information about my iMac and what I experience:
My iMac is a late 2015 Retina 27" with a R9 M380 2048MB graphics card and a 7200RPM drive + upgraded RAM from the 8GB to 24GB by following a guide online and also buying the RAM online(matching the MHz and such of the original RAM).
No amount of taking the Mac to default state by removing RAM or reset of NVRAM and SMC Reset has helped. It does not help to install macOS Sierra onto the internal drive with a 1TB capacity. The only difference is that the boot sequence is slowed down drastically. The Diagnostic Tool (by holding D on boot for a longer time than I initially thought) sends back an "OK" The iMac is stable with no Kernel Panics other than the usual User Error.
The issue:
I recorded a small video in vertical mode what my boot progress looks like - If you look closely you will notice that both the Apple boot logo and the progress bar dissolve as the boot progress takes place.
Previously macOS Sierra got installed from a USB3 key with the installation procedure take from Apple Support website for installing OS X and macOS installers to USB keys. The video is taken with macOS installed from a USB3 key without the upgrade path I use now. macOS Sierra is installed directly onto an external Thunderbolt SSD from LaCie(Rugged model v1) with a Samsung EVO 250GB drive instead of the 120GB drive that was installed from factory(my warranty is long over so I "mauled the casing" by putting in a different brand and size SSD)
The video takes place with the previous installation as mentioned directly above. The currently install* has the same issue - the error just takes place a different place in the boot procedure.
OS X El Capitan installed from Internet Recovery and updated with all available updates after install does not display the glitch on boot. Instead, the screen skips for a second to a black screen with no content and then returns to regular scheduling and gives me the login screen and functions just fine. If the macOS Sierra boot sequence is trying to go black for a second too on boot but instead has the nerve to present me with a dissolve of a logo and progress bar then OK.
Has it become better through updates to macOS Sierra for anyone of you? I personally doubt that Apple is aware of all issues with graphic glitches on all Mac products that has a monitor attached to them like the iMac and all Mac-laptops.
*Currently the installed OS is macOS Sierra 10.12.3 using an upgrade path from OS X El Capitan from Internet Recovery. I'm not going to OS X El Capitan because of this issue - I also doubt that a repair to the iMac will fix anything. If it really was that serious an issue I would have experienced other things that is related to the particular AMD Radeon R9 M380.
I have already mentioned my display and issues with retention and similar in a different thread - this is not related to that. But could be related to either an AMD driver or a macOS fluke. OS X El Capitan behaves better than macOS Sierra.
TL;DR
Please watch the video and comment on your own experiences with similar outcome. Thanks.
Link to video on my Droplr account: http://d.pr/v/Faqf
Continued ...
Here's some information about my iMac and what I experience:
My iMac is a late 2015 Retina 27" with a R9 M380 2048MB graphics card and a 7200RPM drive + upgraded RAM from the 8GB to 24GB by following a guide online and also buying the RAM online(matching the MHz and such of the original RAM).
No amount of taking the Mac to default state by removing RAM or reset of NVRAM and SMC Reset has helped. It does not help to install macOS Sierra onto the internal drive with a 1TB capacity. The only difference is that the boot sequence is slowed down drastically. The Diagnostic Tool (by holding D on boot for a longer time than I initially thought) sends back an "OK" The iMac is stable with no Kernel Panics other than the usual User Error.
The issue:
I recorded a small video in vertical mode what my boot progress looks like - If you look closely you will notice that both the Apple boot logo and the progress bar dissolve as the boot progress takes place.
Previously macOS Sierra got installed from a USB3 key with the installation procedure take from Apple Support website for installing OS X and macOS installers to USB keys. The video is taken with macOS installed from a USB3 key without the upgrade path I use now. macOS Sierra is installed directly onto an external Thunderbolt SSD from LaCie(Rugged model v1) with a Samsung EVO 250GB drive instead of the 120GB drive that was installed from factory(my warranty is long over so I "mauled the casing" by putting in a different brand and size SSD)
The video takes place with the previous installation as mentioned directly above. The currently install* has the same issue - the error just takes place a different place in the boot procedure.
OS X El Capitan installed from Internet Recovery and updated with all available updates after install does not display the glitch on boot. Instead, the screen skips for a second to a black screen with no content and then returns to regular scheduling and gives me the login screen and functions just fine. If the macOS Sierra boot sequence is trying to go black for a second too on boot but instead has the nerve to present me with a dissolve of a logo and progress bar then OK.
Has it become better through updates to macOS Sierra for anyone of you? I personally doubt that Apple is aware of all issues with graphic glitches on all Mac products that has a monitor attached to them like the iMac and all Mac-laptops.
*Currently the installed OS is macOS Sierra 10.12.3 using an upgrade path from OS X El Capitan from Internet Recovery. I'm not going to OS X El Capitan because of this issue - I also doubt that a repair to the iMac will fix anything. If it really was that serious an issue I would have experienced other things that is related to the particular AMD Radeon R9 M380.
I have already mentioned my display and issues with retention and similar in a different thread - this is not related to that. But could be related to either an AMD driver or a macOS fluke. OS X El Capitan behaves better than macOS Sierra.