27-inch iMac EFI FW Update 1.0

Apple’s recent EFI firmware update targets 27-inch iMacs with quad-core Intel Core i5 and Core i7 processors with two bug fixes that address issues with processor loads and the backlit display. The first issue could cause high processor loads when playing audio through the iMac’s headphone jack, while the second could prevent the display backlight from powering on. To install the update, follow the instructions in the updater application that launches automatically after the installer has closed. More information regarding installing a firmware update on an Intel-based Mac is available on Apple’s Web site. The update is available via
Software Update and the Apple Support Downloads page. (Free, 2.1 MB)

Apple has also released a minor SMC firmware update for 27-inch iMacs that addresses unspecified compatibility issues regarding Target Display mode. More information regarding installing SMC firmware updates is available on Apple’s Web site. That update is also available via Software Update and the Apple Support Downloads page. (Free, 397 KB)