Mcgruzoo2
Level 1
(0 points)
Q: Trouble with Target Display Mode on late 2009 27" iMac
Had been using late 2009 iMac 27" in Target Display Mode in conjunction with a Dell XPS tower with i7 CPU, Windows 7, and best graphics card I could afford at the time connected by an HDMI to mini display port cable. Worked fine for years. Put aside Dell for some months and updated iMac to El Capitan OS 10.11.3. Recently tried old setup again with same Dell PC and was able to toggle from Mac to PC, but PC screen resolution was at lowest setting. I got an error message when toggling to PC that said there was a problem with the mini display port causing system to revert to lowest resolution. Unable to reset to higher resolution.
I tested the Dell PC on another monitor, and it works fine at highest resolution (2560 X 1440). When I reconnected to iMac (that works fine), the screen now goes black.
Is it possible the upgraded OS (El Capitan) is incompatible with Target Display Mode using mini display port? Any ideas?
iMac, OS X El Capitan (10.11.3), 3.33Ghz Intel Core 2 Duo
rkaufmann87
Level 9
(58,476 points)
Use your iMac as a display with Target Display Mode - Apple Support, also consider you may have a bad cable or connection. Doesn't hurt to try different cables, they can and do go bad!!!
