BIOS image for the Apple iMac 27-inch Late 2013, logic board 820-3481-A, compressed in a 7.80 MB RAR. Apple numbers its boards in the 820-xxxx format, with the letter suffix denoting revision. Such a dump is written to the EFI/boot ROM SPI chip with a programmer when the firmware is damaged or locked. Apple ROMs contain machine-specific data such as serial number, so dump and keep the original chip contents first and check the image size against the chip capacity.
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 .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →