Apple released a software update for owners of the new 27-inch LED Cinema Displays. The update includes modifications to two OS X system preference panes, which enable brightness and audio features on the new displays.
This update requires OS X 10.6.4 to install. It is also relatively large for a standard display update (75MB download, with around 250MB of replaced system components), but upon looking at the install package, the update not only replaces the specified system preference panes, but also includes new releases of graphics drivers, frameworks, and other video and audio components to update compatibility with the Cinema displays. The update does not install any firmware to the display itself, even though the display will need to be attached when you run the updater.
To install the update, you will need to follow the instructions posted in this Apple Knowledgebase Document (reiterated below):
Connect your Mac to your LED Cinema Display (27-inch).
Your computer and display power cords must be connected and plugged into a working power source.
Save all open documents and quit all other applications.
If you downloaded the disk image using Safari, Safari will notify you that an application is in the image. Click OK to continue.
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 "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.
A license agreement appears. Click Continue to proceed.
Click Agree to accept the terms of the license agreement.
Select a destination to install the software. The destination will be highlighted by a green arrow. Click Continue.
To install the software, click Install.
Enter the computer administrator's password and click OK.
A dialog appears, indicating that this software will require a restart to complete the installation process. Click Continue Installation.
An "Installation was successful" dialog appears. Click Restart.