@Bryce: Yes, booting with only discrete or integrated enabled does solve the problem for me as well.
@Dweia: I patched the CMOS for my 3820TG and unlocked the Intel menu. Now I can choose to only have the IGD activated and PEG (radeon) completely shut off drawing zero power. Same thing as going through vga_switcheroo or using the acpi calls but less hassle.
@Bryce: Yes, booting with only discrete or integrated enabled does solve the problem for me as well.
@Dweia: I patched the CMOS for my 3820TG and unlocked the Intel menu. Now I can choose to only have the IGD activated and PEG (radeon) completely shut off drawing zero power. Same thing as going through vga_switcheroo or using the acpi calls but less hassle.