Over the weekend, Apple released its iMac EFI Firmware Update 1.4 patch for iMac desktops equipped with ATI’s Radeon HD 4850 graphics card. The update, a 1.7 megabyte download (also available via Mac OS X’s Software Update feature) fixes intermittent system freeze issues and fixes wake-from-sleep issues in Boot Camp.
To run the firmware update process, please follow the instructions in the updater application (/Applications/Utilities/iMac EFI Firmware Update.app). The updater will launch automatically when the Installer closes.
After the firmware is successfully applied to your Mac, your Boot ROM Version will be:
IM91.008D.B08.
The update requires Mac OS X 10.5 or later to install and run.