Firmware provides the instructions for the hardware on your Mac to run correctly. The instructions control many low-level functions that affect the power, thermal and sleep management features. Updates to the firmware can also add additional features to your computer and improve the reliability of your hardware. Apple provides new software and updates, including updates to the firmware, through the App Store. If you are unsure whether your Mac's firmware is current, you can check the version number. If it is out of date and an update is not available in the Mac App Store Updates section, you can downloaded and install the current version manually.
Click the Apple menu and select "Software Update" from the drop-down menu. This launches the App Store and automatically sends you to the Updates section. Provide an administrator username and password, if you receive a prompt requesting the information.
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Click the "More" button next to any OS X Update package in the Update section and read the update description to see if any OS X Update packages contain the latest firmware.
Select the "Update" button next to any options that contain firmware updates. Alternatively, click the "Update All" button to update all available software. You may need to provide your administrator username and password again.
Click the Apple menu and select "About This Mac" from the drop-down menu.
Click the "More Info" button.
Select the "System Report" button.
Select the "Hardware" option in the sidebar and note the information in the "Model Identifier" and "Boot ROM Version" section. The Boot ROM Version information refers to the EFI firmware version.
Check the Available Firmware Updates table on the Apple Support website (link in Resources) to determine if you need a newer version of the EFI firmware. If the number for your Boot ROM Version is earlier than the one listed on the website for your Mac, click the link to download the firmware.
Double-click the installation package when it finishes downloading and follow the prompts in the installer to update your Mac's firmware.
Click the "Shut Down" button. After the computer shuts down, hold down the power button until the power indicator light blinks. After you release the power button, a long tone sound and the Apple logo display with a progress bar indicating the progress of the update. The computer restarts and provides you with a message that the update is complete.