updated 02:22 am EDT, Wed July 23, 2014
Can sometimes fail to install, leaving computer unusable
A firmware update, issued on Monday for "Mid-2011" MacBook Air models running OS X 10.9.2 and later, apparently has a bug in either the code or the downloaded file, which is causing reports of system crashes and occasionally a failure to install properly, leaving MBA owners unable to boot the machine. The purpose of the firmware update was to correct two "wake from sleep" issues that affected only "mid-2011" MBAs running 10.9.2 or later. Some users have found that an SMC reset can restore the units to functional status.
Although the problems have been reported to Apple, the company has yet to retract the EFI update or post a patched version. A support thread on Apple's support forums, first noted by AppleInsider, has grown to more than 40 respondents reporting the same problem, with 850 views -- presumably from others looking for a solution.
In the case of an MBA made non-functional but the update, an SMC reset is apparently able to get the unit working again in some cases, but leaves the machine on the previous firmware version. This has lead to a theory that a corrupted download file, rather than a flaw in the EFI update itself, may be responsible for the issues. Some users have reported a successful install of the update, only to find system instability and crashes rather than an inability to boot the machine.
Until Apple can investigate and address the issue, mid-2011 MBA owners should refrain from installing the update. The 4.3MB file can, according to Apple, only be installed over EFI versions 0077.00, 0077.08, 0077.0E and 0077.0F. Users can check what firmware version they are running by going to the Apple menu, selecting "About This Mac," "More info" and "System Report." The new EFI firmware update version is 2.9.