First off, awesome thread here with so much good information. Many thanks to all those who have contributed.
A few months ago I used the instructions in this thread and dosdudes installer to install 10.15.4 on my 2009 iMac. I used the USB Linux flash method to update my video card, and followed the OpenCore instructions to setup the bootloader on an SD card. Everything ran smooth and worked as expected, brightness control ect. The only option I did not install on the unsupported installer was the legacyGPUpatch.
I updated my unsupported installer to 10.15.6 this weekend and had issues after the installation, specifically going to the black screen. I followed the instructions in the latest pdf guide (rev 7/23/2020) and the instructions on the post here (
https://forums.macrumors.com/thread....1596614/page-236?post=28406927#post-28406927) to update the AppleGrapahicsControl.kext with my boardid but my iMac still boots to a black screen unless I hold the option key down to force a boot picker. After installing the patched kext i can not boot to the desktop even with the option key down, loading seems to fail at the launch of the MacOS gui.
So far i have tried the following, all with a fresh install of 10.15.6
-with OpenCore (AppleGrapahicsControl.kext 10.15.6 patched)
-without OpenCore (AppleGrapahicsControl.kext 10.15.6 patched)
-without OpenCore (AppleGrapahicsControl.kext 10.15.4 patched)
-without OpenCore (AppleGrapahicsControl.kext 10.15.6 patched, I updated a fresh version with only my board id Mac-F2268DAE added to the plist)
all seem to give me the same results, either boot to black screen, or if holding option the imac loads until the graphics are supposed to launch. I can ssh into it at that point but the screen is stuck at the apple logo and grey status bar. booting verbos gives errors about AMFI: code signature verification failed and mac_vnode_check. I figured SIP got turned back on so i re-disabled it with my highsierra installer/recovery USB. I still get the same issues.
if I rebuild the kext cache manually or with hackintool after any of the AppleGrapahicsControl.kext modifications (and after using kext utility to install) I get the following
kxld[com.apple.driver.AppleGraphicsDevicePolicy]: The following symbols are unresolved for this kext:
kxld[com.apple.driver.AppleGraphicsDevicePolicy]: agdcGTraceToken(IOFramebuffer const*, unsigned short, bool, unsigned short, unsigned char, unsigned short, unsigned long long, unsigned short, unsigned long long, unsigned short, unsigned long long)
Link failed (error code 5).
Prelink failed for com.apple.driver.AppleGraphicsDevicePolicy; omitting from prelinked kernel.
I assume this is my problem, in that the kext wont load and then the graphics faille to launch the GUI.
any help in this matter would be greatly appreciated. What did I miss here that is causing me soooo much trouble...