My “solution” is different: If the iMac is cold, the screen is black. No problems on the attached monitor, so I set a movie going in VLC and soon the iMac is warm enough to reduce the flickering. [br]
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re the above answer: “If the behavior is there it's part of the VGU/VGC, if it's gone it's a component in your internal display chain.” Does that mean that if there is no problem with the external, its #”a component in your internal display chain”? BUT what does that mean?