Unlocked firmware image for Apple board 820-00138 revision 05, EMC 2909, in 8.00 MB raw binary form. Unlocked typically means the EFI firmware password has been removed so the machine can boot freely after flashing. It is written to the SPI flash chip using a hardware programmer, either with a clip in circuit or after desoldering. Make a full backup of the original chip, confirm the board number on the PCB, and check the flash part is 8 MB so the image fits correctly.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @efibios. Enginerys does not host this file.
How to open a .bin file
A raw, byte-for-byte image of a flash chip: the main BIOS / UEFI, the embedded-controller (EC) firmware, or both.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →