iMac (27-inch, Late 2009): Display flickers and the 27-inch iMac Graphics Firmware Update 1.0

The 27-inch iMac Graphics Firmware Update applies to the graphics firmware on ATI Radeon HD 4670 and 4850 graphics cards to address issues that may cause image corruption or the display to flicker.

This article has been archived and is no longer updated by Apple.

Quit all open applications, then download the update.

  1. The downloader will place the disk image with an installer in your Downloads folder or in the location specified in the General tab under Safari > Preferences.
  2. If you downloaded the disk image via Safari, Safari will notify you that an application is in the image.  Click OK to continue.
  3. If "Open safe files after downloading" is enabled in Safari preferences, the disk image file will mount by itself.  If that preference is not enabled in Safari, double-click the disk image to mount it.

Install the update. Note: you will need the administrator password for the installation.

  1. Some USB and FireWire devices may prevent firmware updates from installing correctly; disconnect non-essential devices and use only an Apple keyboard and mouse to apply the update.
  2. Your computer's power cord must be connected and plugged into a working power source.
  3. In the mounted disk image, double-click the 27-inchiMacGraphicsFWUpdate.pkg file to start the firmware update process.
  4. A welcome screen appears.  Click Continue.  If you receive the message "Your computer does not need this update," your computer is not eligible for this update. 
  5. Follow the onscreen instructions that appear.
  6. An "Installation completed successfully" window appears.  Click Close.
  7. It may take up to 4 minutes to install the update.  You may see a progress dialog appear, indicating the status of the update.  Important: Do not disturb or shut off the power on your iMac during this update. Loss of power could result in your iMac not starting up.
  8. An "Installation completed successfully" window appears.  Click Restart and your computer should restart.

If your computer remains black after applying the update, contact AppleCare or an Apple Authorized Service Provider.  If you continue to experience image corruption or display flickering, make sure you have also installed the 27-inch iMac Display Firmware Update 1.0.  If you still have display image corruption or flicker issues after successfully completing both firmware updates, contact AppleCare or an Apple Authorized Service Provider. 

To determine if the update has already been applied to your computer, follow these steps:

  1. From the Apple () menu in the upper left menu bar, choose About this Mac
  2. Click More Info.
  3. In the hardware section, click Graphics/Displays.
  4. Locate the ROM Revision field.  You should see revision 113-B9110C-425 or 113-B8030F-260 if the update has been successfully applied.
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