Quit all open applications, then download the update.
- 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.
- If you downloaded the disk image via Safari, Safari will notify you that an application is in the image. Click OK to continue.
- 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.
- 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.
- Your computer's power cord must be connected and plugged into a working power source.
- In the mounted disk image, double-click the iMacDisplayUpdate.pkg file to start the firmware update process.
- A welcome screen appears. Click Continue. If you receive the message "Your computer does not need this update," your iMac (27-inch, Late 2009) already has the update installed.
- A license agreement appears. Click Continue. To agree to its terms, click Agree.
- A destination selection screen appears. The software will be installed ont he hard drive indicated by the green arrow. Click Continue, then click Install.
- Enter your administrator password and click OK.
- A dialog appears indicating you will need to restart your computer after installing. Click Continue Installation.
- When the installation is complete, a successful installation message appears. Click Restart to start the update.
- An Apple appears with a progress bar underneath it 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. It may take several minutes for the update to complete.
- Your screen will turn black and your iMac will restart.
If your screen 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 Graphics Firmware Update 1.0. If you are still having display issues after successfully completing both firmware updates, contact AppleCare or an Apple Authorized Service Provider.