https://bugs.freedesktop.org/show_bug.cgi?id=110865
--- Comment #9 from Alex Deucher alexdeucher@gmail.com --- Created attachment 144983 --> https://bugs.freedesktop.org/attachment.cgi?id=144983&action=edit fix DC code
Can you try applying both of these patches? Assuming both of your monitors have the same timing this might work.