updated 02:00 am EDT, Thu September 29, 2011
Fixes intermittent display flickering
Apple has added a firmware update specific to the 24-inch LED Cinema Display that addresses an issue that can cause intermittent flickering when connected to a Thunderbolt-enabled Mac. The update, which does not yet have the normal accompanying technote, may not resolve a flickering issue if a Mini DisplayPort extender cable is used, according to the company. Users on Apple's support forums have been complaining about the flickering problem for months.
The 24-inch LED Cinema Display was available from October 2008 until July 2010. Some buyers were able to pick up refurbished or clearance stock of the monitors for a short period after the discontinuation. Following the discontinuation, Apple sold the 27-inch version for a further year until unveiling the latest iteration in July, whcih dropped the "Cinema Display" brand and is simply called the Thunderbolt Display, since it uses Thunderbolt rather than simply Mini DisplayPort.
The update came to a customer in an official e-mail from Apple France, who cautioned that the patch was still in testing and may not resolve the issue, which is why it hasn't yet been posted publicly. The user shared the link with other 24-inch LED Cinema Display owners who were having the same issue, with most reporting complete success following the application of the firmware, a system reboot and a power cycling of the monitor.
The firmware update should be considered to be on par with beta software and only applied by those with the proper model, running OS X 10.6.8 or later and a Thunderbolt-equipped Mac which demonstrate repeated flickering issues. The note accompanying the update also mentions that some USB and Firewire devices may prevent firmware updates from installing correctly, so those devices should be disconnected before applying the update. Apple keyboards and mice are recommended for use during the update as well.
Apple may be reaching out to affected users directly as testers before publishing the firmware update publicly, perhaps due to some difficulty in reproducing the problem on its own.