BIOS firmware for the Apple iMac A1419, the 27-inch model, on logic board 820-4652-A. The ZIP archive holds an EFI ROM image for rewriting the SPI flash on the logic board with a programmer, which can fix no-boot faults or corrupted firmware. Apple numbers its boards as 820-xxxx with a revision letter, so verify the full code on your board. Before writing, read and save the original chip, since it carries machine-specific data such as the serial number, and confirm the image size matches.
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 @biosarchive. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →