When a SDD or HDD is formatted to use a GUID partition scheme by the Disk Utility or diskutil command, the EFI partition is automatically created.īasically, the firmware update is copied to the FAT32 formatted EFI partition.

Apple posted that firmware updates require a GUID partition scheme at the archived website Firmware updates for Intel-based Macs require a GUID partition scheme, although the site does not explicitly say this must be the primary drive. I assume this EFI partition must be on the primary internal disk. The EFI partition is used when the firmware is updated. Error while writing firmware updater for EFI. disconnect all internal hard drive, connected the USB external drive and SXCARD reader.It selected the ESP on internal hard drive as the staging EFI. kept internal hard drive connected, connected the USB external drive or SXCARD reader.replaced the Samsung SSD with original Apple HDD and tried again.Unfortunately the first one of my MacBook is out of order.Ĭonfirmed the following methods do not work. It seems that the root cause is running OS X from a second internal disk. I've just seem a related post Is there any way to manually bless firmware when main disk is external? In another word, the Boot ROM Version hasn't been changed. Then, 3 times power off automatically in a short period, end up with a normal OS X startup. It got a flashing LED light indicating the firmware was about to be updated. sudo bless -mount / -firmware /MBP91_00D7_B00.scap -verbose -recovery Thus, I've no idea why High Sierra installer failed to update the EFI firmware at the very first time.Īccording to the chapter 2.0 How Does a Mac Update Its EFI Firmware & How Do You Find Your EFI Version of The Apple of Your EFI, with the following command bless, the file MBP91_00D3_B0C_LOCKED.scap extracted from mac2015002efiupdate.dmg, which downloaded from, and the file MBP91_00D7_B00.scap extracted from Install macOS High Sierra.app, it executed successfully. usr/libexec/efiupdater finished with status: 0

Writing firmware update installed cookie (/Volumes/MacSSD/macOS Install Data/.FirmwareUpdateInstalled) Volumes/bless.YdD7/EFI/APPLE/FIRMWARE/MBP91_00D7_B00.scap created successfully If look into previous log of EFI updating, it seems they are quite normal. Operation: Verify firmware failed, Failure Reason: Error Domain= Code=512 Key info in ia.log is as following.Ĭlearing automation and attempting to rebless.įailed to get disk for UUID specified for rebless. Here comes the detail.Īttempt 1 - update it by updating macOS from 10.12.6 to 10.13.2įailed with error message 'An error occurred while verifying firmware'. In short, the firmware cannot be updated either by upgrading macOS to High Sierra or by bless manually.

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