strange an 27" 2011 core i7 imac, with upgraded GTX765M, is having some strange black screen problems latly.
It is still running MacOS High Sierra latest version and updates, with an GTX765M vbios beta 3.
Problem is that the screen will remain black very often, after a cold boot and normal warm boots/reboots.
When I remote into the iMac, the display is recognized but in a strange way.
Anyway, when I shutdown the iMac, and startup again using the option key, to force the bootscreen the display is working great again.
Im not sure if this problem has been posted here before, that High Sierra (native supported OS) is also giving these black screen problems, but i'm almos certain that after an security update perhaps apple broke something here.. ?
if I am correct somebody else here said to replace a modded kext file ( AppleGraphicsControl.kext ? ), could perhaps also fix this black screen problem for High Sierra.. ?
And I'm sorry if a solution has already been posted here, than I have missed that one..
I hope somebody here can help us out. thanks in advance,
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I'm uploading a patched AppleGrapahicsControl.kext that is now necessary as of 10.15.4, the symptoms after this update are a blank screen but system sounds are heard when holding down the Escape key, as well a loss of any Displayport output. The cause of this is Apple Clamping down on 3rd party kexts from loading, this mainly affects hackintosh users, but affects us as our iMacs are no longer a supported platform.
What does this patched AppleGraphicsControl.kext do to allow 2009-2011 iMacs to properly boot? We now need our board ID's to be added to the AppleGraphicsDevicePolicy.kext within AppleGraphicsControl.kext, this allows the kext to properly load on boot, before this wasn't necessarily needed. I have so far all known 5 board ID's that are supported on our thread.
| iMac12,2 | (27-inch Mid 2011) | Mac-942B59F58194171B |
| iMac12,1 | (21.5-inch Mid 2011) | Mac-942B5BF58194151B |
| iMac11,3 | (27-inch Mid 2010) | Mac-F2238BAE |
| iMac11,2 | (21.5-inch Mid 2010) | Mac-F2238AC8 |
| iMac11,1 | (27-inch Late 2009) | Mac-F2268DAE |
Thanks to
@Ausdauersportler for the helping/testing for this kext.
To install this kext unlock your System partition using Hackintool. drag the kext on-top of the kext utility icon let it install/timeout with an error. Open terminal and enter "sudo reboot" skipping this step may leave your iMac hanging at the desktop (A Catalina issue)
How to install:
When booting you need to Hold Alt/Option to bring up the AppleBootPicker, then select the Catalina partition. Since the iMac's Screen is on when using AppleBootPicker the Macs screen will remain on the entire boot process allowing you to log in and then proceed to install the Patched AppleGraphicsControl Kext.
perhaps this or a similar fix is also out there for High Sierra.. ?
We are recently experiencing these same issues on HS..
Perhaps you already posted a fix for this, I dont know.. ?
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I was told that even High Sierra may have the black screen issue after the May, 2020 upgrade. But this happens after booting into the MacOS and not on reboot with the EFI boot screen. The AppleGraphicsControl extension can help with HS!
The vBIOS of the Nvidia has a delay which leads to the behavior you discovered: The screen (without choosing alt/option to have a boot screen) remains black some seconds and after that you see suddenly the login screen. This is normal.
But you should have the EFI boot screen on boot (pressing and holding the option key while pressing power button) and you should use OpenCore to get the brightness control. Without the LCD will cook slowly your iMac 🙂
BTW:
Using OpenCore with the MacPro1,1 ID makes the black screen issue disappear, even with Nvidia systems.
We indeed are experiencing also black screen issues with High Sierra latly, I think after the latest High Sierra security update.
I'm almost sure that the 2020-003 is giving these problems.. ?
You already found a fix for HS perhaps.. ?
