Apple's Recently Announced iMacs Receive a Software Update
Apple recently released an Extensible Firmware Interface update for the late 2013 models of the iMac that were recently announced. The update brings the EFI for the latest 2013 iMacs to version 2.1. It’s aimed at addressing an issue that sometimes occurred when installing Windows 7 or Windows 8 using the Boot Camp Assistant.
Previously if both an external optical drive and USB thumb drive were connected to the system, the installation process could cause a black screen to appear. This has been resolved with the recently released update. Additionally, the update makes sure that a system will boot by default into OS X after installing Windows 8.
The iMac (late 2013) EFI Update 2.1 is available as a free 8.7 MB download from Apple’s support pages. It is also important to note that it requires a Mac that is running OS X Mountain Lion version 10.8.4 (12E4022) or later.