I'm trying to set up dual displays for the first time ever. I have a Mac Pro 2.66 Quad-Core, OS 10.6.4, ATI Radeon HD 4870. My display is an older (but still perfectly fine) Apple Cinema HD 23" display.
Today I purchased a Dell 23" LED monitor and have connected its HDMI output to the Radeon's Mini DisplayPort with an adaptor, and am completely unable to make things work. I spent quite a bit of time with Dell and they swear that the display is fine, but I'm still stuck.
When I connect the Dell, the Dell does nothing, but the Cinema Display changes to show only the splash screen that comes up when you first log in....except there aren't accounts from which to choose...only the splash screen. I see my mouse moving around on the screen, but can't get anything else to show up on the screen know matter how many key combinations I try. If I disconnect the Dell, the Cinema Display returns to normal.
Dell had me diconnect the Cinema Display and use only the Dell....nothing. The light on the Dell indicates that it's getting power, but pushing the power button on the screen doesn't do anything.
I figured out that, when both monitors connected, I can push the display button on the Cinema Display and get to the Displays preferences screen. At first, I see only the Display Preferences window exactly as it's always looked, but when I "gather windows" I get two windows...one is the usual window for the Cinema Displa with the Display, Color and Options tabs. The other is for the Dell and this one has the added Display, Arrangment and Color tabs.
When I play with the options in the Cinema Display window, it behaves like it did when there's only one display and the Dell window disappears. When I play with the options in the Dell window, the Cinema Display looks distorted....apparently the Dell settings are being applied to the Cinema Display. When I'm in the Dell window and go to the "Arrangment" tab, I see the two images repesenting the two monitors. I can move those around in the manner described in the Mac documentation....that affects the Cinema Display and can move things off the screen, but the Dell remains black and silent. When I select the "Mirror" button, the two images in the Display window are stacked on top of each other....both with a menu bar at the top of their windows. The Cinema Display looks like normal, but again, the Dell remains black.
I have no clue what to try next. The Dell has never turned on, though it IS receivne powerl Help?