Every once in a while, Apple releases firmware updates for various Mac models. The firmware updates are designed to correct a known problem, such as the 2012 MacBook Air EFI firmware update, which corrected issues with video over the HDMI port.
Finding your Mac's Model Identifier
Firmware updates are easy to apply, but occasionally something can go wrong. The most common causes of problems are a power outage, accidentally shutting down your Mac before an update is complete, or any other type of event that interrupts the update process. The end result is a Mac that may not start up.
Many newer Macs are able to self-recover from a bad firmware update, but if you have a Mac that's a few years old, you'll need a special Firmware Restoration CD in order to restore your Mac to an operational state.
In this guide, we show you where to download the restoration CD files, how to create the CD, and how to restore the firmware. You may never need this CD, but if you do, you'll be glad to have it on hand.