https://bugs.freedesktop.org/show_bug.cgi?id=107823
--- Comment #11 from raxondmc@gmail.com --- Your correct, sorry i missed the dc=0 comment.
Seems like you have Carrizo->DP2DVI(PASSIVE)->NEC monitor?
Do you if other monitors show it as well?
I will try with my 580x and a dongle and can let you know. (albeit different monitor).