iMac EFI Update 2.0
This update is recommended for the iMac (21.5-inch, Late 2012).
This update contains general performance fixes pertaining to sleep and Thunderbolt, and improves compatibility when using the 5GHz band in Wi-Fi.
Boot ROM or SMC Version Information: After Update is complete:
Build version: 010A.05
ROM version: IM131.88Z.010A.B05.1211151146