MacBookPro integrated graphics card issue.
First, It caused repeated black screen. I could barely start with boot-args="agc=-1" option.
After 3 times of os-re-install and numerous PRAM reset, now, I can boot without "agc=-1", but the system always use dedicated GPU (750m).
Whenever I try to activate 'automatic gpu switching', system crashes.
I think something happened with integrated intel graphics card.
Is it possible to corrupted PRAM (maybe... since I deleted EFI completely before my last OS re-install) cause selective iGPU failure?