I have two monitors, one DVI and one HDMI. After switching to Radeon, putting the computer into sleep makes the HDMI display show a very long "Check Cable Connection" message instead of going into sleep mode. This is problematic at night, because even though the screen is black, this is a "bright" black with backlight. So the room is illuminated for about 10 additional minutes. This did not happen with Intel graphics. (The DVI monitor goes into sleep mode, as before.)
I have tried "NirCmd" monitor off, and it made the HDMI display go to sleep mode immediately. But when I created a batch file that first turned the monitors off and then put the computer to sleep, the same thing happened: the HDMI monitor showed Check Cable Connection".
Is there any solution? Or is this not a generic problem, but of my HDMI monitor, or my Radeon card of a specific manufacturer (hardware issue)?