Kbase Article of the Week: About EFI and SMC firmware updates for Intel-based Mac computers →

Apple Support:

This article lists firmware updates available as standalone installers for Intel-based Mac computers.

Most firmware updates are automatically installed when you update or upgrade OS X. Some firmware updates are also available as downloads you can install manually. If your Mac needs a firmware update and it isn’t installed automatically, check to see if a manual updater is listed below.