Apple today also released 27-inch iMac EFI FW Update 1.0 which is recommended for all quad-core Intel Core i5 and Core i7 processors 27-inch iMacs.
This update addresses the following:
• Resolves an issue that sometimes caused high processor utilization while playing audio through the headphone output mini-jack.
• Resolves an issue that prevented the display backlight from turning on after powering on the iMac.
Note: When your computer restarts a gray screen will appear with a status bar to indicate the progress of the update. Do not disturb or shut off the power on your iMac during this update.
27-inch iMac SMC Firmware Update 1.0 and 27-inch iMac EFI FW Update 1.0 are available via Software Update and also as standalone installers.
[Thanks to MacDailyNews Reader “Fred Mertz” for the heads up.]