10.14.6 Update Changed my BIOS

[singj]

I just had an unpleasant, but ultimately successful, upgrade on my daughter's machine (i5-9400, Gigabyte H310M A 2.0, AMD MSI 580, headless iGPU and two HDMI monitors). I don't really understand how this could have happened, but here goes:

Attempted to upgrade via Software Update from 10.14.5. At first reboot, something was obviously wacky with Clover (usually go from black screen to version info, then drive select, without artifacts). Now, the slash and underscore characters were flashing on the screen for a moment - low resolution (big) characters in upper left, then closer to the center, a few times before posting the Clover version info then drive select screen.

Select the "Install..." option and the Apple logo appears with a progress bar. After a couple of moment, both of my displays flash once and go black. (Both have signal, but a black screen). After a long time (15+ minutes), the computer reboots to Clover (same artifacts again). No "Install..." option this time, which is weird because there should have been at least one more "Install..." option for the update, from what I've read.

So - I choose "Boot Mojave" and Apple logo, progress bar reappears. It inches forward for a few seconds, then both displays go black. Monitor #2 starts flashing at regular intervals, like a metronome. Monitor #1 flashes occasionally. I leave the computer like this for over a half hour. It apparently boots all the way into 10.14.6, as I will later find a Time Machine backup with this OS revision, but I can't see anything except intermittent flashing on either monitor.

I use my rescue USB installer to boot. This boots without issue; I roll back my installation to 10.14.5 via Time Machine.

On reboot, I notice the same artifacts pre-Clover boot screen. As the restored 10.14.5 installation boots, both monitors flash once, then start flashing intermittently as they'd done before. I am experiencing distress at this point. I may have used some colorful language.

I try booting 10.14.5 from the USB drive by hitting F12 at boot. I point the USB drive at the restored 10.14.5 installation. It boots without a single issue.

At this point I'm thinking - OK, something with the installer tinkered with the EFI partition (there was a note about changes to booting into Boot Camp). I recopy the EFI folder from my USB drive onto my Mojave SSD. Restart and...

...same Clover artifacts, flashing displays on boot.

Try from USB drive again: no issues, boots cleanly into 10.14.5. Did the installer mess with the SSD firmware or something?

Earlier posts encouraged trying the Combo installer. I download and run it. On the first restart, the artifacts are present as Clover starts up. I repeat verbatim the issues I had with my first attempt.

This time, after waiting at the black screen for a while, I force shutdown. On a lark, I try using F12 to boot from the SSD. To my amazement, it works! No video issues - as I try to boot into Mojave it finishes the installation (12 minutes remaining) and everything is working perfectly under 10.14.6.

Looking in BIOS - my drive settings in BIOS have been totally rewritten from what they were prior to attempting the installation. BIOS has been trying to boot Clover as P0 instead of UEFI. I repopulate the boot list, and everything is lovely again.

I guess what I'm trying to say is this:

Either something about the update actually caused my BIOS to change / reset, or through some incredible fluke the Boot priority settings (and *only* those settings) coincidentally changed during or right before I ran the update. Once I reset the BIOS to see my UEFI SSD installation, all was well.

Something for people to check who are having trouble with black screens.

 

[wladdych]

Smooth update. Still have the purple horizontal line glitch. Everything seems to work.

Read my post on insanelymac/whatevergreen support how to fix this. Or just try latest whatevergreen from repository.