6 Replies Latest reply: Oct 18, 2014 7:07 PM by Buddyboy4
ultraspiracle Level 1 Level 1 (0 points)

A periodic flicker exists in an external Dell ST2410 that is attached to this computer via the DVI connector and, importantly, occurs ONLY since upgrading from Lion 10.7.5 to 10.8.4 one day ago.  Besides the flicker, the external display will occasionally go completely blank for 1-2 seconds. This is reproducible (weirdly) when the central air conditioning turns on in my apartment. This does not occur with the internal color LCD. Flicker occurs regardless of whether computer is connected to AC power via magsafe.


Important that it occurs only since 10.8.4; not sure if this existed in previous iterations of OS X.


Disabling automatic graphics switching does not affect the occurrence of the flicker.



System logs do not show anything.



Resolution of external monitor is 1920x1080



Hardware Overview:



  Model Name:          MacBook Pro

  Model Identifier:          MacBookPro9,1

  Processor Name:          Intel Core i7

  Processor Speed:          2.7 GHz

  Number of Processors:          1

  Total Number of Cores:          4

  L2 Cache (per Core):          256 KB

  L3 Cache:          8 MB

  Memory:          16 GB

  Boot ROM Version:          MBP91.00D3.B08

  SMC Version (system):          2.1f170

  Serial Number (system):

  Hardware UUID:          7A534DAA-7147-598D-AD15-595884440804

  Sudden Motion Sensor:

  State:          Enabled






  System Version:          OS X 10.8.4 (12E55)

  Kernel Version:          Darwin 12.4.0

  Boot Volume:          500GB SolidState

  Boot Mode:          Normal



  Secure Virtual Memory:          Enabled

  Time since boot:          1:27


Anyone have any suggestions?


Many thanks!

MacBook Pro (15-inch, Mid 2012), OS X Mountain Lion (10.8.1)
  • iriverav82 Level 1 Level 1 (0 points)

    I'm experiencing a similar problem with this 10.8.4 update.


    I have a 2010 white macbook and an LG 23EA63 external monitor. I had no issues whatsoever with 10.8.3, but when I updated my system to 10.8.4, the computer began booting in safemode and then the external monitor would start showing flashes of light of approx. 2-3 inches randomly across the screen.


    These problems only occur when using the external monitor. If I unplug it and start my computer with the built-in screen only, then I have no issues.


    I read in another post that a guy solved it by switching to an original Apple Minidisplay-to-VGA adapter. He was using an alternative brand before, that apparently the new 10.8.4 update didn't recognize. I'll try with that and let you know how it goes.

  • Eric Root Level 8 Level 8 (36,610 points)



    Video Troubleshooting Internal and External Monitors


    You can also try booting into the Safe Mode to see if the problem is there also.  Shut down the computer and then power it back up. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application unistaller. For each disable/delete, you will need to restart if you don't do them all at once.


    Safe Mode


    Safe Mode - About

  • iriverav82 Level 1 Level 1 (0 points)

    Update: I bought an original Apple Mini Displayport to VGA adapter and that solved the flickering/flashing issue I had.

  • amishsteve Level 1 Level 1 (0 points)



    I am running 10.7.5 on a 11" Macbook Air with a SyncMaster PX2370 using an HDMI with an additional Thunderbolt to HDMI adapter.  I recently starting getting the flicker, blue screen on my Mac, white snow, black out on my ext. screen.  All the common symptoms - driving my crazy turning the Mac on/off, plugging and unplugging the HDMI cable to get the Mac to recognize the ext. monitor. 


    Bottom line I figured I was adding to the complexity of the problem w/ the adapter to the HDMI, etc.


    Fix: I ordered a single cable (HDMI to Thunderport aka Mini Display) for $11.95 on Amazon and that has completely FIXED the problem. 

  • MeLarry Level 1 Level 1 (0 points)



    I shouldn't have to purchase anything to get to work what was working before the update.

    Very frustrating.

  • Buddyboy4 Level 1 Level 1 (0 points)

    I too had a double issue.  The external Samsung monitor would have a flicker about once every 20 seconds and often would go black for one second then come back.  Anything I typed while black was still there when it came back.  Both were cured by replacing the HDMI cable from the monitor to the case.  I replaced an HDMI to HDMI cable with a HDMI to a DVI at the case.  The cure was instant.  Maybe that will help someone.  OSX 10.9.5   Graphics  Intel HD Graphics 4600 1536 MB