Downgrade from Big Sur to Mojave - Success

[jpz4085]

Still no progress. Although I formatted my primary SSD using the Recovery volume on my secondary disk, attempting to boot on my installer disk immediately results in a restart, putting me on the secondary SSD's Recovery volume.

It would appear that if I want to install Mojave, I will have to reformat my secondary SSD as well.

Just remove or disable any SSDs other than the target. No need to wipe them unnecessarily. I'd suggest clearing the NVRAM from the OpenCore menu too. Then give the install another try.

 

[wstrohm]

Just remove or disable any SSDs other than the target.

Um... these are M.2 SSDs, and the one not already wiped is on the bottom of my motherboard (i.e.underneath). I will try clearing NVRAM... not sure that will help, though. And I can disable booting from it in my BIOS, which I have done, but it makes no difference. In what other way can I "disable" it without wiping it?

 

[jpz4085]

Um... these are M.2 SSDs, and the one not already wiped is on the bottom of my motherboard (i.e.underneath). I will try clearing NVRAM... not sure that will help, though. And I can disable booting from it in my BIOS, which I have done, but it makes no difference. In what other way can I "disable" it without wiping it?

Well, the point is to prevent the other SSD from being visible at all. While individual SATA ports can usually be disabled in the BIOS I'm not sure about M.2 so removing it might be a the only option. Check your motherboard manual. Clearing the NVRAM will at least eliminate the parameters from the previous macOS installations.

 

[wstrohm]

I gave up and formatted both Samsung 970 SSDs in my computer at left. Then I attempted to install first Mojave (failed), and then High Sierra (failed).

Lack of progress baffles me. Twice, I created my Mojave installer from scratch, and twice, OpenCore displays the "Install Mojave" icon, I select and click on it, get a nice Apple (but no progress bar), and then the computer restarts to a black screen and sits there doing nothing. The High Sierra installer just gives me a slashed circle. Only my Big Sur installer can be successfully opened and it gives me all the normal options... Disk Utility, Terminal, Re-install Big Sur, etc.

I tried making an installer with a blank EFI folder, since the "create installer" routine does not put anything in the EFI partition, although the volume itself is there after formatting the USB. All that does is repeatedly restart the computer, over and over, when trying to boot the installer. Of course then there is no OpenCore, which at least shows the icon for the installer when OC is present.

Any further thoughts? Am I somehow forced to re-install Big Sur? Or is there something I need to change in OpenCore (0.7.5) to get the Mojave installer to open? config.plist change(s) maybe?

 

[jpz4085]

I gave up and formatted both Samsung 970 SSDs in my computer at left. Then I attempted to install first Mojave (failed), and then High Sierra (failed).

Correct me if I misunderstand the situation. Were you able to successfully boot the Mojave installer just once on the first attempt but not again or has it not worked the entire time? Have you ever loaded Mojave or High Sierra successfully before this attempt?

Lack of progress baffles me. Twice, I created my Mojave installer from scratch, and twice, OpenCore displays the "Install Mojave" icon, I select and click on it, get a nice Apple (but no progress bar), and then the computer restarts to a black screen and sits there doing nothing. The High Sierra installer just gives me a slashed circle. Only my Big Sur installer can be successfully opened and it gives me all the normal options... Disk Utility, Terminal, Re-install Big Sur, etc.

Boot the either installer in verbose mode so we can see where in the loading process the problem occurs. You want to add -v to the NVRAM 7C436110-AB2A-4BBB-A880-FE41995C9F82 boot-args section in your config.plist. Also enable Kernel-Quirks-PanicNoKextDump if not already so if there's a panic the cause should be visible. Attach the EFI folder you're using along with pictures of the potential errors in the kernel loading text.

I tried making an installer with a blank EFI folder, since the "create installer" routine does not put anything in the EFI partition, although the volume itself is there after formatting the USB. All that does is repeatedly restart the computer, over and over, when trying to boot the installer. Of course then there is no OpenCore, which at least shows the icon for the installer when OC is present.

To be expected. Nothing unusual.

Any further thoughts? Am I somehow forced to re-install Big Sur? Or is there something I need to change in OpenCore (0.7.5) to get the Mojave installer to open? config.plist change(s) maybe?

It does sound like changes to config.plist may be needed. We should be able to tell more about what's happening with verbose mode enabled then see where to go from there.

 

[wstrohm]

Correct me if I misunderstand the situation. Were you able to successfully boot the Mojave installer just once on the first attempt but not again or has it not worked the entire time?

Depends what you mean here by "boot." I plug in the installer USB, in the BIOS choose it and disable both the SSDs (both are blank, but the SSDs are still listed in the BIOS). Then Save and Exit the BIOS. I get the AMI display, then the OpenCore display which shows the "Install macOS Mojave" icon (plus "NVRAM" and "EFI" icons). Then I click on the installer icon and an Apple appears, but no progress bar. Then the Apple disappears, and I am left with nothing but the cursor in the upper left corner of a black display. This happens with an EFI folder in the installer flash drive that is identical to the one I always used in this computer when it had Big Sur installed. I have not seen another behavior since first attempting this installation. I am beginning to wonder if the installer does not contain a required driver for the RX 580 graphics card, and the installer app is in fact opening, but not sending a picture to the monitor. However my monitor usually indicates when it is not receiving a video signal, and I'm not seeing that message.

At one point I removed the RX 580, changed the DisplayPort output to the motherboard's built-in connector and changed the "Initial Graphics" from "PCie" to "IGFX." No change.

I will add "-v" boot argument to the NVRAM area and enable that quirk you mentioned above. (I've never had much luck with "-v" because it all goes by so fast and then leaves so quickly. But I'll try it.)

[Edit: No joy, same thing. Apple for about 5 seconds, then it disappears and black screen. I tried this with "IGFX" and internal graphics enabled, but I still don't get any text on screen or anything other than black. My next trick is to change Device Properties/Add/AAPL,ig-platform-id argument from "0000913E" (means internal graphics is used only for computing and does not drive a display) to "00093BE" which seems to be one solution to a black screen problem. Also added the frame buffer patch for Whatever Green.]

[Edit 2: My next trick made no change. Just for fun, I booted the installer on my High Sierra (also Coffeelake computer, "Mini-ITX 3" below), and got the error message "This version of Mac OS X is not compatible with this platform." Which is odd, I thought, because I could easily update to Mojave from my High Sierra computer using Software Update. Right?]

 

[wstrohm]

So I changed my "Generic" section SMBIOS in OpenCore from iMac19,1 to iMac18,3. Then I selected this Mojave installer as my startup disk in my High Sierra computer, and it works fine there, i.e. I could install Mojave in my "Mini-ITX 3" below if I wanted. Not doing that, of course. Back to my Mini-ITX 4 computer at left, I booted (i.e.selected the Mojave installer USB as boot device) while using the motherboard graphics (with the "-v" in the OC boot arguments). What happens is that after the initial boot, and the Apple icon coming up and disappearing, my black screen contains "End Set Console Mode" or some such. No other verbiage, and it is placed in the upper left corner of the screen. After a while it reboots, and the same thing shows up. I have no idea what this means or what to do next. This did not occur before I changed my SMBIOS from iMac19,1 to iMac18,3.

[Edit: Changing SMBIOS back from iMac18,3 to iMac19,1 and plugging the installer back into my computer at left, for some reason now displays the standard "-v" boot argument text when I "boot" the installer. So now, same as I always remember, there is this HUGE incomprehensible text zipping up my display, stopping in places, then going again until finally it races out of sight. How can I get anything from this? Have my wife make a video on her iPhone?]

 

[jpz4085]

Depends what you mean here by "boot." I plug in the installer USB, in the BIOS choose it and disable both the SSDs (both are blank, but the SSDs are still listed in the BIOS). Then Save and Exit the BIOS. I get the AMI display, then the OpenCore display which shows the "Install macOS Mojave" icon (plus "NVRAM" and "EFI" icons). Then I click on the installer icon and an Apple appears, but no progress bar. Then the Apple disappears, and I am left with nothing but the cursor in the upper left corner of a black display. This happens with an EFI folder in the installer flash drive that is identical to the one I always used in this computer when it had Big Sur installed. I have not seen another behavior since first attempting this installation.

OK, that answers my question. You've never been able to load the installer after selecting it from OpenCore.

[Edit: Changing SMBIOS back from iMac18,3 to iMac19,1 and plugging the installer back into my computer at left, for some reason now displays the standard "-v" boot argument text when I "boot" the installer. So now, same as I always remember, there is this HUGE incomprehensible text zipping up my display, stopping in places, then going again until finally it races out of sight. How can I get anything from this? Have my wife make a video on her iPhone?]

Yes, you want a picture - not necessarily a video - of the final screenful of text. The relevant error(s) should be near the end. Post the picture so I and others can get more information about what's happening.

 

[wstrohm]

'OK, that answers my question. You've never been able to load the installer after selecting it from OpenCore."

Well, not quite true. It loads properly from OpenCore on my High Sierra computer (connected to the monitor's HDMI input).

Okay, what is the probability that the Mojave MacOS Installer.app does not support DisplayPort? Never mind, I'm going to switch to HDMI and see if that makes a difference.

[Edit: HDMI connection to monitor gives the same results; clearly that's not the problem. So will plead with wife to take a pic or video.]

 

[wstrohm]

Here is a zipped jpeg still picture of the last frame of a 65 MB MP4 video from my wife's iPhone. It was taken after I hit keyboard "return" on the Install Mojave.app icon. I have the video which consists of over 1500 frames. I can take a still pic of any of them, but which ones are the question. Some are very blurry because of the speed of scrolling during the video... those frames are not very readable. What else can I do?