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My Mac Pro Desk Top computer no longer can "see" my second display??

389 Views 7 Replies Latest reply: Dec 31, 2012 7:10 PM by saratoga lefty RSS Branched to a new discussion.
saratoga lefty Calculating status...
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Dec 31, 2012 7:48 AM

I've tried reversing the connections on the back of the MacPro but it still doesn't "see" the second display.  I've had these two displays hooked up for years with no problems.  I recently upgraded to Mountain Lion and I just had the MacPro in the Apple Store for a  "One To One" transfer of data to my new MacBook Pro laptop.  When I brought it back home it still worked fine.  I then was cleaning up some stuff and I know I went into my "Users and Groups" panel in System Preferences and I did remove some items from the "Login Items" list that open automatically so maybe that is the problem??  I know the second display is getting power and recognizes it's connection to the compuiter because when I disconnect it, it says, "no signal" and when I reconnect it, it just goes to sleep.  Advice appreciated.


Saratoga Lefty

Mac Pro, OS X Mountain Lion (10.8.2)
  • Grant Bennet-Alder Level 8 Level 8 (48,110 points)

    What graphics card?


    Two DVI displays? Any Mini DisplayPort ? Any adapters in use?


    Is one (or both) wider that 1920 wide?

    Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
  • Grant Bennet-Alder Level 8 Level 8 (48,110 points)

    Thanks for providing additional information. Since you did not answer my specific, pointed questions about connection and the exact reolution of these displays, I will have to look them up ... later.

    Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers
  • Grant Bennet-Alder Level 8 Level 8 (48,110 points)

    Some of the graphics cards that had two DVI connectors had one Dual-Link (suitable for all resolutions including wider than 1920 wide) and one Single-Link (suitable for resolutions up to 1920, but not wider). This does not appear to be your problem, since both are less than 1920 wide.


    The "Drivers" business is a complete Red Herring (Not Applicable), as the Mac does not use Drivers for displays -- it uses a unified driver for the Display CARD, and customizes it based on the capabilities reported by the Display when connected. In order to get this to work, the display must correctly self-identify.


    To verify that the display is correctly detected, look in:


    About This Mac > ( More Info ) > Graphics and Displays ...


    ... a correctly self-identified display shows its Name and its maximum resolution. be skeptical, this information does not update when you plug/unplug the display, and you have to close and re-open this window (or possibly the entire program) to get the information to refresh after a change.


    If either display provides a USB cord, it must be plugged in to complete the display connection and provide display ID and control (this is much more common with Apple displays that third-party displays).


    Is there any evidence of trauma to the display connectors or cables? Any bent pins on the connectors?

    Mac Pro (Early 2009), Mac OS X (10.6.8), & Server, PPC, & AppleTalk Printers


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