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I am one of the ones experiencing pixel problems on my late 2013 iMac. Has anyone tried uninstalling Yosimite and reinstalling Mavericks to solve the problem?

My iMac info - iMac (27 inch, Late 2012) Processor 3.4HHz Intel i7 Memory 32 GB 1600 MHz DDR3 Graphics NVIDIA GeForce GTX 680MX 2048 MB


I experienced pixels which were spread across the screen and then flickering of triangle shape glitches. After doing a google search I realized that I am not alone on this recent problem. I possible solution without some patch or update from Apple was to uninstall Yosemite. My question is, has anyone done this yet and had it solve a pixel problem which may be affecting the graphic card software? This would require an install of Mavericks.

Imac, Mac OS X (10.5.5)

Posted on May 22, 2015 1:16 PM

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1 reply

May 22, 2015 1:28 PM in response to Ronnok

If indeed it is a bug in Yosemite, then you can only downgrade to Mavericks if you happen to have either a Mavericks installer application or a clean and complete backup of Mavericks. If these aren't possible for you then you will have to downgrade to Mountain Lion because Mavericks is no longer available.


Purchase a redemption code at the Online Apple Store: OS X Mountain Lion. Mountain Lion is $19.99 plus tax. Use the code to redeem a download of Mountain Lion from the App Store. The file is quite large, over 4 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.


Or you can try a clean install of Yosemite by erasing the drive then reinstalling Yosemite.


Install or Reinstall OS X from Scratch


Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.


Boot to the Recovery HD:


Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.


Erase the hard drive:


1. Select Disk Utility from the main menu and click on the Continue button.


2. After DU loads select your startup volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.


3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.


4. Quit DU and return to the main menu.


Reinstall OS X: Select Reinstall OS X and click on the Install button.


Note: You will need an active Internet connection. I suggest using Ethernet if possible

because it is three times faster than wireless.


This should install the version of OS X that you had installed.

I am one of the ones experiencing pixel problems on my late 2013 iMac. Has anyone tried uninstalling Yosimite and reinstalling Mavericks to solve the problem?

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