This can't be good! |
It turns out a major problem with older macs is the AMD GPU eats itself and prevents bootup. You have two options: go to the Apple Store and pay big dollars for a new graphics card, or disable the GPU.
If you decide to disable the GPU, just know that 3D applications that normally use the GPU will be slow. But for normal operations, your Mac will work fine.
Here is the procedure I successfully used:
Reset the SMC
Shutdown, unplug everything except power and hold
leftShift + Ctrl + Option + Power
Hold this for 5 seconds
Reset NVRAM: Power up and hold
Command + Option + p + r
Until you hear the startup chime two times.
Shutdown computer
Power up and boot into Single User Recovery by holding
if you are on high sierra 10.13.6+ you might need to useCommand + r
instead
Command + r + s
On the screen that loads choose a language. Next, on the screen which appears next choose the following options in the menu Utilities -> Terminal (see below.)
In the terminal that comes up, type the following commands:
Disable SIP (This is slow)
csrutil disable
Disable Discrete GPU on boot by running
nvram fa4ce28d-b62f-4c99-9cc3-6815686e30f9:gpu-power-prefs=%01
Reboot
reboot
Boot into Single User-mode by holding
Command + s
It might look as if it hanged, but press enter and you should see the shell (root#)
Mount root partition writeable
/sbin/mount -uw /
Make a kext-backup directory
mkdir -p /System/Library/Extensions-off
Move ONLY ONE offending kext out of the way
mv /System/Library/Extensions/AMDRadeonX3000.kext /System/Library/Extensions-off/
Inform the system to update its kextcache:
touch /System/Library/Extensions/
Reboot
reboot